Finely divided ionomer coated thermoplastic resin

ABSTRACT

Powders of thermoplastic resins such as polyethylene homopolymer and ethylene-vinyl acetate copolymer are obtained by agitating molten resin in admixture with water and in the presence of a dispersing amount of a substantially water insoluble ionomer polymer.

This is a division of application Ser. No. 205,838, filed Nov. 10, 1980,now U.S. Pat. No. 4,336,210.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention belongs to the field of processes for providingthermoplastic resins in fine powder form and, more particularly, to suchprocesses in which the powders are obtained from aqueous dispersions ofresin.

2. Description of the Prior Art

Thermoplastic resins in finely-divided form have found use in a numberof applications where it is either impossible or inconvenient to utilizethe more conventional cube or pellet forms. For example, powderedorganic polymeric thermoplastic resins in dry form have been used tocoat articles by dip coating in either a static or fluidized bed, bypowder coating wherein the powder is applied by spraying or dusting, andby flame spraying. In dispersed form, thermoplastic resin powders havebeen applied as coatings by roller coating, spray coating, slushcoating, and dip coating to substrates such as metal, paper, paperboard,and the like. These powders have also been widely employed inconventional powder molding techniques. Other applications of thesepowders include paper pulp additives; mold release agents for rubber;additives to waxes, paints, and polishes; binders for non-woven fabrics;dry-blendable impact modifier powders; and so on.

It is well known that high molecular weight thermoplastic resins, forexample, polyethylene and ethylene copolymers, may be converted todispersions of spherically shaped particles which are substantiallydevoid of particles greater than 25 microns in diameter and in which thenumber average particle diameter is less than about 10 microns. Thus,McClain, U.S. Pat. No. 3,422,049, teaches that such dispersions offinely divided particles may readily be prepared by agitating the moltenresin in admixture with water at elevated temperatures and atautogeneous pressure, in the presence of certain dispersing agents whichare particular block copolymers of ethylene oxide and propylene oxide.Such dispersing agents are available commercially under the trade namePluronic (BASF-Wyandotte Corp.). Unless the thermoplastic resin is asoft, tacky material that is prone to coalesce under ambient conditions,the nonagglomerated spherical particles can be recovered as powders bycooling the dispersions below about 100° C. and collecting the suspendedmaterial by filtration or centrifugation.

U.S. Pat. No. 3,418,265 teaches that the particle size of suchthermoplastic resin dispersions can be reduced still further, to thesubmicron level, while retaining the unique spherical particle shape byincluding in the dispersion process a volatile, inert, water-insolubleorganic liquid that is soluble in the thermoplastic resin in an amountbetween 0.5 to 20 parts per 100 parts of the resin, whereupon a stable,aqueous, film-forming latex is ultimately obtained as the final product.Alternatively, U.S. Pat. No. 3,522,036 teaches that stable, film-formingaqueous latices of high molecular weight polyethylene can also be formedby including a liquid vinyl monomer such as styrene in the dispersionprocess.

Although the foregoing dispersion procedures are conveniently operatedas batch processes, it is also known to produce such finely dividedpowders in a sequential, continuous process. See, e.g., U.S. Pat. No.3,432,483.

U.S. Pat. No. 3,586,654 teaches that it is further possible to conductthe dispersion process in such a way that the polymer particles may befurther transformed into spherical particles of controlled average sizeand size distributions which are the same, larger or smaller than thestarting particles. If desired, the dispersion process can be modifiedin such a manner as to produce spherical foamed particles (U.S. Pat. No.3,472,801), or to incorporate within the particles certain colorants(U.S. Pat. No. 3,449,291) and pigments (U.S. Pat. No. 3,674,736). Inaddition, it has been found that various substrates can be coated byapplying the above described dispersions of polyolefin fine powders inan inert carrier, heating to evaporate the carrier, and fusing thepolyolefin to the substrate (U.S. Pat. No. 3,432,339). Further, U.S.Pat. No. 3,669,922 teaches a process for preparing colored polymerpowders having controlled charge and printing characteristics of valueas toners in electrostatic printing.

In the above cited art, the dispersing agents, as block copolymers ofethylene oxide and propylene oxide with molecular weights of about 3,500to as much as 16,250, belong to the class of oligomeric or low molecularweight polymeric dispersing agents, as opposed to the more familiar,conventional dispersing agents such as, for example, fatty acid soaps,sodium lauryl sulfate, etc. For many years it appeared that theaforesaid block copolymers of ethylene oxide and propylene oxide werethe only substances capable of directly dispersing high molecular weightthermoplastic resins, especially olefin polymers, in water at elevatedtemperatures.

Recently, however, it has been shown that certain soaps of the highestacids available commercially, e.g., lithium behenate, are by themselvesalso capable of dispersing polyethylene (U.S. Pat. No. 4,148,768).Alkali metal soaps of fatty acids such as stearic acid, oleic acid,palmitic acid, myristic acid, etc. are at best only marginally effectivein dispersing polyethylene and are quite ineffective in producingpolyethylene dispersions at the high resin concentrations and highproduction rates attainable with the ethylene oxide-propylene oxidecopolymer dispersants disclosed above. The alkali metal soaps of thesaid fatty acids can, however, be made to disperse polyethylene andethylene-vinyl acetate copolymers containing up to about 15 weightpercent of vinyl acetate, at rates and at solids levels comparable tothose achievable wit the Pluronics, if said soaps are produced from thefatty acid and alkali in situ during the dispersion process and in thepresence of a water-soluble neutral salt; e.g., sodium chloride, sodiumsulfate (U.S. Pat. No. 4,148,766). When ethylene-vinyl acetatecopolymers containing about 15 to 35 weight percent of vinyl acetate aredispersed, however, a preformed alkali metal fatty acid soap, in thepresence of a water-soluble neutral salt, may then be used as thedispersant system (U.S. Pat. No. 4,151,133), and if the ethylene-vinylacetate copolymer contains above about 35 weight percent of vinylacetate, the soap alone is a satisfactory dispersing agent, optionallyin the presence of a water-soluble neutral salt to control particle size(U.S. Pat. No. 4,150,003).

As pointed out above, block copolymers of ethylene oxide and propyleneoxide as dispersants produce spherical particles with a number averageparticle diameter less than about 10 microns. In general, particlediameter is affected very little by process variables. By contrast,however, the aforesaid newly described soap-salt dispersant systemsproduce larger spherical particles, with few particles having diametersbelow 20 microns being observed. Particle size in the soap-saltdispersion system can be varied to some degree by varying the nature ofthe soap and especially the concentration of the water-soluble neutralsalt. Increasing the soap concentration beyond some threshold value haslittle effect on particle size. Adding alkali beyond the point ofneutralization of the fatty acid favors binodal particle sizedistributions.

Truly high molecular weight dispersing agents have recently beenemployed to disperse olefinic polymers (U.S. Pat. No. 4,174,335), butthe process of that patent is clearly directed to the production ofstable aqueous dispersions, and not to the dispersion of such resinsinto particle size ranges that would lend themselves to recovery as drypowders. Thus, according to U.S. Pat. No. 4,174,335, stable aqueousdispersions are produced by mixing a molten blend of (a) a carboxyl-freeolefin resin and (b) a carboxyl-containing olefin resin with an aqueousmedium in the presence of at least 0.2 chemical equivalent, to thecarboxyl groups, of a base. Typically, aqueous dispersions stable up toseven days at room temperature are produced, the ultrafine particles ofwhich are spherical and no more than 3 microns in diameter. Largerparticles were obtained only when the process was operated at too low adispersion temperature (120° C.) or when less than 0.2 equivalent ofbase per equivalent carboxyl groups was used, or when the acid number ofthe carboxyl-contaning olefin resin was less than 20. As explained morefully hereinafter, the process of U.S. Pat. No. 4,174,335 is totallyunsuited to making olefin polymer powders of the previously cited art,and especially of the present invention, because the rates of dispersionare exceedingly slow. Moreover, the ultrafine particles produced are toofine for easy isolation, handling and application.

SUMMARY OF THE INVENTION

In accordance with this invention, a normally solid thermoplastic resinis rapidly dispersed under conditions of rapid mixing in water heated toa temperature at or above the melting point of the resin, employing asdispersing agent at least one substantially water-insoluble ionomerpolymer, and following cooling of the aqueous dispersion to atemperature which is below about 100° C., the resin is recoveredtherefrom as a finely divided powder. The use of substantiallywater-insoluble ionomer polymers as dispersing agents herein generallyprovides resin particles which are larger than those obtained by the useof the block copolymers of ethylene oxide and propylene oxide heretoforeemployed as dispersing agents, and more comparable in size to thoseproduced by the aforesaid soap-salt dispersant systems, while at thesame time affording a wider choice of process variables for controllingparticle size and particle size distribution than is possible with thelatter dispersants without, however, requiring the use of large amountsof dispersant. In addition, the dispersing agents herein substantiallyavoid the objectionable respirable dusts (air-borne particles 10 micronsor less in diameter) that can at times be created from powders producedby the aforementioned block copolymers of ethylene oxide and propyleneoxide.

Briefly stated, the invention herein provides a process for preparing infinely divided form a solid organic polymeric thermoplastic resin whichcomprises: (a) agitating a mixture of the resin while in the moltenstate, a dispersion-forming amount of water, and a dispersion-formingamount of a substantially water-insoluble ionomer polymer, to provide anaqueous dispersion of the resin; and, (b) cooling the dispersion tobelow about 100° C. to provide solid particles of resin.

The cooled dispersion of resin powder can be directly employed invarious applications or the resin powder can be recovered therefromusing known and conventional procedures such as filtration andcentrifugation.

The term "ionomer polymer" as used herein defines an ionic copolymer ofat least 50 mol percent of an ethylenically unsaturated alpha-olefin of2 to 10 carbon atoms, from about 0.2 to about 50 mol percent of analpha, beta-ethylenically unsaturated carboxylic acid having from 3 to 8carbon atoms, and optionally, other ethylenically unsaturate comonomers,said copolymers having from 10% to 100% of the carboxylic acid groups insalt form with metal ions. The foregoing copolymers and methods fortheir preparation are now well-known, e.g., as disclosed in U.S. Pat.Nos. 3,264,272 and 3,322,734, both of which are incorporated byreference herein, and various types are commercially available from E.I. DuPont de Nemours and Company as the Surlyn ionomer resins.

Functional derivatives of the alpha, beta-ethylenically unsaturatedcarboxylic acid copolymer resins, e.g., their lower alkyl esters, theiramides, imides, may also be converted to the ionomer polymers as definedherein, by known processes of partial or complete saponification orhydrolysis.

The ionomer may be produced in situ during the dispersion process, froma copolymer of an alpha-olefin and an alpha, beta-unsaturated carboxylicacid and an alkali added to the aqueous dispersion medium. Exemplarythereof is the use of ethylene-acrylic acid copolymers in the presenceof an aqueous dispersion medium containing sodium hydroxide. Suchethylene-acrylic acid copolymers are available, for example, from DowChemical Co.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In general, the polymers suitable for the practice of this inventioninclude any normally solid synthetic organic polymeric thermoplasticresin whose decomposition point is somewhat higher than its meltingpoint and somewhat less than the critical temperature of water. Includedare polyolefins, vinyls, olefin-vinyl copolymers, olefinallylcopolymers, polyamides, acrylics, polystyrenes, cellulosics, polyestersand fluorocarbons.

The polyolefins most suitable for the practice of this invention includenormally solid polymers of olefins, particularly mono-alpha olefins,which comprise from two to about six carbon atoms, e.g., polyethylene,polypropylene, polybutene, polyisobutylene, poly(4-methylpentene), andthe like. Preferred polyolefin feeds are polyethylene and polypropylene.

Vinyl polymers suitable for use in this invention include polyvinylchloride, polyvinyl fluoride, vinyl chloride/vinyl acetate copolymers,and polyvinylidene dichloride and difluoride.

Suitable olefin-vinyl copolymers include ethylene-vinyl acetate,ethylene-vinyl propionate, ethylene-vinyl isobutyrate, ethylene-vinylalcohol, ethylene-methyl acrylate, and ethylene-ethyl methacrylate.Especially preferred are ethylene-vinyl acetate copolymers wherein theethylene constitutes at least about 25%, preferably at least about 50%,of the copolymer by weight.

Olefin-allyl copolymers include ethylene-allyl alcohol, ethylene-allylacetate, ethylene-allyl ether, ethylene-acrolein, and the like.Ethylene-allyl alcohol is especially preferred.

Preferred among the polyamides are linear superpolyamide resins,commonly referred to as nylons. Such polymers can be made by theintermolecular condensation of linear diamines containing from 6 to 10carbon atoms with linear dicarboxylic acids containing from 2 to 10carbon atoms. Equally well, the superpolyamides may be made fromamide-forming derivatives of these monomers such as esters, acidchlorides, amine salts, etc. Also suitable are superpolyamides made bythe intramolecular polymerization of omega-amino-acids containing 4 to12 carbon atoms and of their amide-forming derivatives, particularly thelactams. Examples of specific nylons are polyhexamethylene adipamide,polyhexamethylene sebacamide, and polycaprolactam. Especially preferredar nylons having intrinsic viscosities ranging between 0.3 to 3.5 dl./g.determined in m-cresol.

Acrylic resins suitable for use in this invention include polymethylmethacrylate, polyacrylonitrile, polymethyl acrylate, polyethylmethacrylate, etc. Preferred is polymethyl methacrylate.

The ionomer polymer dispersing agents of this invention are anionic,substantially water-insoluble random (but occasionally alternating orblock) copolymers having an average molecular weight of about 10,000 toabout 1,000,000 or even higher, and preferably, from about 10,000 to300,000. The resins herein can be obtained by copolymerizing a firstethylenically unsaturated compound selected from the group consisting ofmono-olefins and diolefins of from 2 to 10 carbon atoms, vinylaromatics, vinyl esters and vinyl ethers, and a second olefinicallyunsaturated compound selected from the group consisting of an alpha,beta-ethylenically unsaturated carboxylic acid or alpha,beta-ethylenically unsaturated sulfonic acid of from 3 to 8 carbon atomsto provide a copolymer containing at least 50 mol percent polymerized ofthe first ethylenically unsaturated compound and from 0.2 to 50 molpercent polymerized alpha, beta-ethylenically unsaturated carboxylic orsulfonic acid and thereafter reacting the copolymers with an ionizablemetal compound which results in the formation of the ionomer.Alternatively, the resins herein can be prepared by graft copolymerizingfrom about 3 to about 30 weight percent, and preferably from about 5 toabout 15 weight percent, of an alpha, beta-ethylenically unsaturatedcarboxylic or sulfonic acid onto an ethylenic homopolymer or copolymerand reacting the resulting resins with ionizable metal compounds. Wherethe sulfonic acid-containing base resins are concerned, anotherprocedure for preparing the dispersants herein involves introducing in aknown manner sulfonic acid groups into an ethylenic unsaturatedhomopolymer or copolymer and reacting the sulfonated resins with anionizable metal compound.

Monoolefins which can be employed in the formation of the ionomerpolymers include ethylene, propylene, butene-1, pentene-1, hexene-1,3-methylbutene-1, 4-methylpentene-1, and so on. Diolefins which can beused herein include butadiene, isoprene, 2,3-dimethylbutadine,2-chlorobutadiene, 2-fluorobutadiene, and the like. Useful vinylaromatics include styrene, alpha-methyl styrene, vinyl toluene and vinylnaphthalene. Among the vinyl esters which can be used to prepare theionomer resins are vinyl acetate, vinyl propionate, vinyl butyrate,vinyl trimethylacetate, vinyl pelargonate, vinyl decanoate, vinyllaurate, vinyl palmitate, and vinyl stearate. Useful vinyl ethermonomers include methyl vinyl ether, ethyl vinyl ether, isopropyl vinylether, n-butyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether,and the like.

Among the alpha, beta-ethylenically unsaturated carboxylic acids whichcan be reacted with the monoolefins, diolefins, vinyl esters and vinylethers above-cited, to form the copolymers for conversion to theionomeric polymer dispersing agents of this invention, are acrylic acid,methacrylic acid, ethacrylic acid, itaconic acid, maleic acid, fumaricacid, monoesters of dicarboxylic acids such as methyl hydrogen maleate,methyl hydrogen fumarate and ethyl hydrogen fumarate and the chemicallyequivalent acid anhydrides such as maleic anhydride. Vinyl sulfonic acidcan be copolymerized with ethylenically unsaturated monomer (s) toprovide the copolymer resins herein; alternatively, sulfonic acid groupscan be introduced into an unsaturated polymer or copolymer by reactingthe latter with acetyl sulfate, or a sulfur trioxide complex of dioxaneor tetrahydrofuran or by using any other known sulfonation technique.

Metal ions which are advantageously employed in the formation of theionomeric copolymers can be selected from among the uncomplexed andcomplexed ions as described in U.S. Pat. No. 3,264,272 which isincorporated herein by reference for the disclosure of suitable metalions. Examples of useful uncomplexed metal ions are the mono-, di- andtrivalent ions of the metals of Groups I, II, III, IV-A and VIII of thePeriodic Table of the Elements. Suitable monovalent metal ions are thoseof sodium, potassium, lithium, cesium, silver, mercury and copper.Suitable divalent metal ions are those of beryllium, magnesium, calcium,strontium, barium, copper, cadmium, mercury, tin, lead, iron, cobalt,nickel and zinc. Suitable trivalent metal ions are those of aluminum,chromium, iron and yttrium. Alkali metal ions are preferred. Theionomer-producing reaction is conveniently carried out by blending thecarboxylic or sulfonic acid copolymers with a sufficient amount of metalcompound calculated to result in neutralization of at least 10 percentof the acid groups present in the copolymer chain and separating theresulting ionomeric copolymers. The carboxylic or sulfonicacid-containing copolymer and the metal compound for converting it tothe ionomeric form may be blended in a separate operation, as in aBanbury mill; in an extruder, especially in a multi-screw extruder; in acontinuous mixer, or on a two-roll rubber mill. If desired, the blendingmay be done in a separate dispersion operation, wherein the carboxylicor sulfonic acid-containing copolymer, or a functional derivativethereof, e.g., a lower alkyl ester, amide or imide, is fed to an aqueoussolution of alkali, sufficient for neutralization or saponification, toyield an aqueous dispersion of the desired ionomeric dispersant. Theaqueous dispersion of ionomeric polymer thus produced can thereafter befed as a separate stream to provide the polymeric dispersant fordispersing thermoplastic resins according to the process of thisinvention.

Alternatively, the carboxylic or sulfonic acid-containing copolymer forproducing the ionomer dispersing resin may be fed directly to thedispersion vessel, separate from the thermoplastic resin to bedispersed, or it may be blended or mixed with the thermoplastic resinand then fed to the dispersion reactor, where, in either case,sufficient alkali is present to at least effect a 10 to 100%neutralization of the acid groups present.

When the degree of neutralization is increased, the particle sizedistribution generally becomes narrower. For ionomer dispersing resinsof higher initial carboxylic acid content, particle size shifts to finerparticle sizes. For dispersing resins of lower carboxylic acid content,narrowing of particle size tends to occur at larger particle sizes.Thus, degree of neutralization provides a means of controlling particlesize.

The ionomer polymer dispersing agents of the present invention, byfunctioning effectively from temperatures as low as the melting point oflow density polyethylene, i.e., about 115° C., up to as high as 325° C.are not limited to the dispersion of low molecular weight low densitypolyethylenes. For example, high molecular weight, low densitypolyethylenes; linear polyethylene; polypropylene, polyvinyl chloride,ethylene-vinyl acetate copolymers; ethylene-allyl alcohol copolymers;nylon; and the like, can be readily dispersed by means of the subjectnovel dispersing agents to dispersions substantially devoid of particleslarger than 800 microns and wherein the particle size can be controlledto have a relatively narrow particle size range.

The temperature of operation is dependent upon the melting point, meltflow properties, decompostion temperature, and desired particle size andparticle size distribution of the selected synthetic organicthermoplastic resin and ionomer polymer dispersing agent. While theforegoing can be dispersed at temperatures commencing with theirrespective melting point, increases in dispersion temperature beyond themelting point and up to the decomposition of the resins are generallyaccompanied by corresponding increases in the fluidity of the moltenresin. As the fluidity of the melt increases, the dispersions generallytend to develop lower average particle sizes without requiring increasesin agitation effort.

The dispersing apparatus or device may be any device capable ofdelivering at least a moderate amount of shearing action under elevatedtemperatures and pressures to a liquid mixture. Suitable, for example,are conventional autoclaves equipped with conventional propellerstirrers. Propellers designed to impart greater shear to the mixture,e.g., toothed disc impellers can also be employed. The particle size anddistribution are dependent on the stirring rate, high stirring speedsresulting in finer and narrower dispersions until an optimum speed isreached above which there is little change. In general, the rate ofstirring can vary from about 1200 to about 4000 rpm and preferably fromabout 1800 to about 3800 rpm. Stirring rates lower than these can besufficient for a particular dispersion medium and higher rates, whileoperable, are usually without advantage. The dispersion appears to beformed almost instantaneously, at the moment the stirrer is firststarted upon reaching dispersion temperature in batch operation, or whenthe resins enter the dispersion zone in continuous operation. Broadly,the stirring periods will range from about 1 to 20 minutes andpreferably from about 5 to 15 minutes. The stirring period, ordispersion time as defined above, has relatively little effect onparticle size when polyolefins are dispersed, but shifts in particlesize may be observed when more polar polymers are dispersed. In theprocess of this invention, and in the aforesaid prior art involving theproduction of resin powders by dispersion in water wherein thedispersing agent is a block copolymer of ethylene oxide and propyleneoxide, or a soap-salt system, as a consequence of the almostinstantaneous nature of the dispersion process, the maximum solid level(25% or more) of dispersed resin is reached equally fast. This nearlyinstantaneous build-up to maximum solids may be contrasted with theprocess of U.S. Pat. No. 4,174,335 wherein comparable solids levels arereached only slowly, over periods of an hour or more, and whereadditional stirring periods are routinely employed. It will beunderstood, however, that the stirring rates and periods will dependupon the type of equipment utilized.

A very important characteristic, therefore, of the powder-making processof this invention and, in general, of all the above-cited powder-makingart, is the rate at which the total olefin polymer or copolymer andionomeric dispersing resin is converted to the dispersed finely-dividedform. Broadly, the rate will range from at least 200 g. of total resinper liter of aqueous medium per 10 minutes to as much as 20,000 g. ofresin per liter of aqueous medium per 10 minutes, preferably from about400 g. to 1500 g. of total resin per liter of aqueous medium per 10minutes. The highest possible rates are desirable if polymer powders areto be manufactured at lowest costs in a plant of any given size.

These high rates may be contrasted with the much lower rates of 1-100 g.of resin dispersed per liter of aqueous medium per 10 minutes disclosedin U.S. Pat. No. 4,174,335, wherein the final product is not a powderbut a stable latex of ultrafine particles. Moreover, it is clear that inactual fact these rates of 1-100 g. must be scaled down still further toat most 0.25 to 25 g. of resin dispersed per liter of aqueous medium per10 minutes because an additional stirring time of at least 30 minutes attemperature is specified in U.S. Pat. No. 4,174,335 after the completionof the period over which the resin is fed to the dispersion vessel.Therefore, the rates of the present powder-making process and of theabove-cited related processes are at least ten times greater than thoseof U.S. Pat. No. 4,174,335.

In carrying out the subject process, the selected synthetic organicthermoplastic polymer is first contacted with water and the dispersingagent. It is a particularly advantageous feature of this invention thatthe dispersing agent need not be incorporated into the polymer prior tothe introduction of the water by such means as melting and the like asin U.S. Pat. No. 4,174,335, but may be introduced into the dispersingapparatus simultaneously with the other ingredients or as a dispersionin the aqueous phase. Example 12 hereinbelow in fact shows that attemptsto disperse pre-blended mixtures of low density polyethylene and acommercially available ionomer in the sodium form (Surlyn 1555) resultin unacceptably coarse dispersions or in no dispersion at all.Alternatively, separate addition of the copolymer required for producingthe ionomeric dispersing resin, e.g. an ethylene-acrylic acid copolymer,is also possible, but, in this method of operation, sufficient alkalimust also be fed to convert, in situ during the dispersion process, saidcopolymer into the corresponding ionomeric dispersing resin. Separatefeeding of the thermoplastic resin to be dispersed and the ionomericdispersing resin, in one of the above-described operational variants, isgenerally to be preferred.

An outstanding advantage of such separate feeding of the two resins isthat the ionomeric dispersing resin appears to accumulate on the surfaceof the dispersed particles of thermoplastic resin. This is evidenced bythe fact that when the latter is a soft, tacky material such as anethylene-vinyl acetate copolymer containing about 35 weight percent ormore of vinyl acetate, a dispersed product is formed that can berecovered by filtration, dried and handled as a compaction-resistant drypowder. The dry powder is suitable for dry-blending into rigid polyvinylchloride formulations where it functions as an impact strength improver.The same ethylene-vinyl acetate copolymers, when dispersed with theblock copolymers of ethylene oxide and propylene oxide of the art,cannot even be recovered as discrete particles since the particlessubstantially coalesce upon filtration.

It is, of course, possible to blend the thermoplastic resin to bedispersed with the dispersing resin prior to the dispersion process,said procedure being an integral part of the comparatively slow processof U.S. Pat. No. 4,174,335 for making stable dispersions of ultrafineparticles. The advantages of doing so, in the high rate process formaking coarser powders of controlled particle size distribution of thepresent invention, are not impressive and can substantially be matchedby suitable adjustment of one or more of the dispersion processvariables when the resins are fed separately.

In particular, when in the process of the present invention, thepreferred separate feeding of the two resins is replaced with thefeeding of blends of the two resins, as is practiced in U.S. Pat. No.4,174,335, there is no appearance of the ultrafine less-than-3 micronparticles thereof. Rather, as shown in Examples 9 and 10 hereinbelow,using a partially neutralized ethylene-acrylic acid dispersing resin,blend feeding leads to only modest shifts to finer particle fractions,substantially all greater than 10 microns in diameter, and somenarrowing of particle size distribution. And again, with acommercially-available ionomer resin (Surlyn 1555) richer in carboxylicacid content, separate feeding yields fine dispersions (Example 4),whereas blend feeding, as pointed out above, yields very coarseparticles or no dispersion at all (Example 12). Addition of an alkali tothe dispersion medium, however, which presumably augments the degree ofneutralization of the said ionomer, will lead to dispersions where poorresults were obtained without the added alkali (Example 13), but theparticle sizes are still coarser in these blend-feeding experiments thanwhen separate feeding was used, as in Example 4.

If desired, the dispersion process may be operated in a continuousmanner, in which case it is convenient to continuously introduce thedesired ratio of ionomeric dispersing agent, water, and thermoplasticresin in separate streams to the reactor while continuously removingfrom another part of the reactor the product dispersion.

The amount of water used in relation to the sum total of ionomericdispersing resin and thermoplastic resin being dispersed generallyranges from about 0.1 to about 10.0 parts by weight of water per part oftotal normally solid resin. Lower ratios, although usable, presentoperational difficulties. The preferred range is between about 1.0 toabout 5.0 parts per part of resin. The ratio of water to total resinsolids has a strong effect on particle size and particle sizedistribution. Lowering the ratio toward unity can lead to a narrowing ofparticle size with a shift to finer particle sizes and in factrepresents a parameter for controlling particle size and particle sizedistribution as is shown in Example 6 hereinbelow.

The amount of ionomer polymer dispersing agent should be sufficient toprovide a dispersion of the resin in the water under the selectedconditions. Very good dispersions can be obtained at amounts within therange of from 2 to about 50 weight parts by weight of dispersing agentper 100 weight parts by weight of thermoplastic resin and amounts of 5to about 25 parts by weight are preferred. An increase in the ratio ofionomeric dispersing resin to the thermoplastic resin narrows particlesize distribution. For ionomeric dispersing resins of higher carboxylicacid content, the narrowing of particle size will occur at finerparticle sizes, other factors being equal, as shown in Examples 4, 7 and8. Therefore, particle size and particle size distribution can becontrolled to a considerable extent by varying the ratio of ionomerdispersing resin to the thermoplastic resin. There is no upper limit onthe amount of dispersing agent which can be employed except thatexceeding the amount beyond that required to provide an acceptabledispersion may be economically wasteful.

The temperature for forming the hot aqueous resin dispersion can rangefrom about 100° C. to about 270° C. with temperatures of from about 150°C. to about 250° C. being preferred. Most preferred is a temperature of200° C. to 250° C. Increasing the dispersion temperature from 200° C. to250° C. can result in a narrowing of particle size distribution atintermediate particle size ranges for ethylene-vinyl acetate copolymers(Example 2). Thus, dispersion temperature is another parameter that canbe used to control particle size and particle size distribution.

The pressure under which the present process is carried out is adjustedto exceed the vapor pressure of water at the operating temperature so asto maintain a liquid water phase. More particularly, the pressures mayrange from about 1 to 217 atmospheres, and preferably from about 6 to120 atmospheres. In cases where the resin is sensitive to air at theelevated dispersion temperature, an inert gas, e.g., nitrogen or helium,may be substituted for the air normally present, and deaerated waterused. When heat-sensitive polymers, e.g., polyvinyl chloride, are to bedispersed, heat stabilizers in sufficient amounts can be included in thedispersion process. Plasticizers, lubricants, antioxidants, and the likecan also be included. Mixtures of polymers are also suitable fordispersion in accordance with the process of this invention.

The process of the present invention provides a method for rapidlyconverting thermoplastic resins to fine powders via dispersion in water.In rate of production it compares favorably with the previouslymentioned process of U.S. Pat. No. 3,422,049 and the continuous processbased thereon, described in U.S. Pat. No. 3,432,483, and also theprocesses of U.S. Pat. Nos. 4,168,768; 4,148,766; 4,151,133; and4,150,003. It differs radically from the process of U.S. Pat. No.4,174,335, which is directed to the production of stable aqueousdispersions of ultrafine particles, produced at much slower rates.

In the accompanying Tables A-1 and A-2, the process of this invention iscontrasted with that of U.S. Pat. No. 4,174,335.

                                      TABLE A-1                                   __________________________________________________________________________                          Intrinsic             Intrinsic                                      Den-     Viscosity,                                                                         Amount,     Amount,                                                                            Viscosity,                                                                             NaOH--                                                                             Aqueous                          sity                                                                             Index [η]                                                                            g.          g.   [η]                                                                             Acid                                                                             COOH'                                                                              Medium              Process of                                                                           Type  g/cc                                                                             g/10 Min.                                                                           /1/  /15/ Type   /15/ /1/   No.                                                                              Molar                                                                              ml.                 __________________________________________________________________________    U.S. Pat. No.                                                                 4,174,335                                                                     Example 2                                                                            Ethylene-                                                                           0.940                                                                            /4/   1.0  20,500                                                                             Ethylene-                                                                            1,500                                                                              0.13  75 0.89 60,000                     Butene-1              (142.5)                                                                          Acrylic                                                                               (7.5)                                                                 Acid                                                                          Copolymer                                     Example 5                                                                            Ethylene-                                                                           0.920                                                                            /4/   0.7  27,000                                                                             Ethylene-                                                                            3,000                                                                              0.5   62 1.0  60,000                     Propylene           (135)                                                                              Methacrylic                                                                          (15)                                          Copolymer                Acid                                                                          Copolymer                                     This                                                                          Invention                                                                     Example 9                                                                            Poly- 0.915                                                                            22     0.85                                                                              136  Ethylene-                                                                            14     0.61/2/                                                                           39 0.64 450                 Exp. 2 ethylene                 Acrylic                                                                       Copolymer                                                                     (Dow                                                                          PE 459)                                       Example 13                                                                           Poly- 0.915                                                                            22     0.85                                                                              136  Ethylene-                                                                            14   0.31  64 1.18 450                 Exp. 2 ethylene                 Methacrylic                                                                   Acid                                                                          Copolymer                                                                     Ionomer                                                                       (Surlyn 1555)                                 Example 17                                                                           Poly- 0.962                                                                            28    1.0    142.5                                                                            Ethylene-                                                                             7.5 0.31  64 0.89 45                         ethylene                 Methacrylic                                                                   Acid                                                                          Copolymer                                                                     Ionomer                                                                       (Surlyn 1555)                                 __________________________________________________________________________

                                      TABLE A-2                                   __________________________________________________________________________                                           Rates                                                                               Rate of                                                                       Making                                  Dispersion Conditions           Resin Dispersed                                             Im-     Resin                                                                              Addi-                                                                              Feed Rate,                                                                          Material                                              peller  Addition                                                                           tional                                                                             g     g     Yield Average                                Stir-                                                                            Tip     Time,                                                                              Stirring                                                                           Liter ·                                                                    Liter ·                                                                    of    Particle                    Vessel and rer                                                                              Speed                                                                             Temp.,                                                                            Min.,                                                                              Time,                                                                              10 Min.                                                                             10 Min.                                                                             Powder,                                                                             Size,                Process of                                                                           Stirring   rpm                                                                              ft/min.                                                                           °C.                                                                        /12/ Min. /7/   /7,8/ %     Microns              __________________________________________________________________________    U.S. Pat. No.                                                                 4,174,335                                                                     Example 2                                                                            100-liter Pressure                                                                         500                                                                              /10/                                                                            200 180  60   27.8  20.9  Powder                                                                              <1                          Vessel with Turbine                         Not                               Stirrer /9/                                 Recovered                  Example 5                                                                            100-liter Pressure                                                                         500                                                                             /10/                                                                             170 180  60   27.8  20.9  Powder                                                                              <0.9                        Vessel with Turbine                         Not                               Stirrer /9/                                 Recovered                  This                                                                          Invention                                                                     Example 9                                                                            1-liter Parr Reactor                                                                     3,700                                                                            2,900                                                                             200  15  None 222   222   100%  93% >53              Exp. 2 4-in. internal                                                                diameter, two-toothed                                                         disc turbines, 3-in.                                                          diameter                                                               Example 13                                                                           1-liter Parr Reactor                                                                     3,700                                                                            2,900                                                                             200  15  None 222   222   100%  100% >10             Exp. 2 4-in. internal                                                                diameter, two-toothed                                                         disc turbines, 3-in.                                                          diameter                                                               Example 17                                                                           1-liter Parr Reactor                                                                     3,700                                                                            2,900                                                                             200  15  None 222   222   100%   97% > 106                  4-in. internal                                                                diameter, two-toothed                                                         disc turbines, 3-in.                                                          diameter                                                               __________________________________________________________________________

Although the comparisons shown in tables A1 and A-2 are not identicalwith regard to the thermoplastic resins used therein, these resins areall polyolefins or olefinic copolymers and are of similar molecularweight as measured by intrinsic viscosity. The ionomeric dispersingresins are of comparable structure and not too different in acid numberand their degrees of neutralization are comparable, as are the ratios ofthermoplastic resin to ionomeric dispersing resin. In all cases theseresins were blended before dispersion, at temperatures near the meltingpoint of the higher melting resin or just above. However, in theexamples of U.S. Pat. No. 4,174,335 as shown in the upper part of TablesA-1 and A-2, the slow resin addition rates inherent in that process wereemployed, whereas in the examples in the lower part of Tables A-1 andA-2, the rapid addition rates of the present process are employed. It isclear that resin addition rate alone accounts for the great disparity inparticle size produced by the two processes, i.e. ultrafine, less-than-3micron particles in the process of U.S. Pat. No. 4,174,335 and the muchlarger particles of the present invention. As to the effect of agitationon particle size, in U.S. Pat. No. 4,174,335 it is stated that for theproduction of stable dispersions of ultrafine, less-than-3 micronparticles, vigorous mechanical stirring must be applied as the meltblend of resins is slowly added to the aqueous alkaline medium. Suchvigorous agitation is defined therein in terms of impeller powerrequirement per unit volume, and power number and discharge number ofthe impeller. No information is provided as to the geometry and size ofthe impellers used; only stirrer speeds are provided (Table A-2), whichrange from 500-5000 rpm.

Tables B-1 and B-2 which follow summarize representative examples fromboth batch and continuous operation with the Pluronic dispersants whereresin solids level, ratio of dispersant to resin, and especially therapid dispersion times are comparable to the process of the presentinvention.

                                      TABLE B-1                                   __________________________________________________________________________            Resin                                                                                      Melt Flow                                                                           Intrinsic Dispersant                                                                              Aqueous                                        Density,                                                                           Rate, Viscosity                                                                          Amount,   Amount,                                                                            Medium,                        Process of                                                                            Type    g/cc g/10 Min.                                                                           /1/  g.   Type g.   ml                             __________________________________________________________________________    U.S. Pat. No.                                                                 3,422,049                                                                     Example I (A)                                                                         Polyethylene                                                                          0.915                                                                              22    0.85 300  Pluronic                                                                           18   273                                                                 F-98                                                                          /3/                                      Example IV                                                                            Polyethylene                                                                          0.915                                                                              22    0.85 300  Pluronic                                                                           27   373                                                                 F-108                                                                         /5/                                      Example VI                                                                            Polyethylene                                                                          0.915                                                                              22    0.85 300  Pluronic                                                                           27   273                                                                 F-108                                    Example V                                                                             Polyethylene                                                                          0.915                                                                              22    0.85 300  Pluronic                                                                           27   273                                                                 F-108                                    Example X                                                                             Polyethylene                                                                          0.965                                                                              22    --   300  Pluronic                                                                           27   273                                                                 F-108                                    Example XIII                                                                          Polypropylene                                                                         0.905                                                                              7     --   300  Pluronic                                                                           27   273                                                                 F-108                                    Example XIV                                                                           Ethylene-vinyl                                                                        0.95 25    --   300  Pluronic                                                                           27   273                                    Acetate /13/                 F-108                                    U.S. Pat. No..                                                                3,432,483                                                                     Example I                                                                             Polyethylene                                                                          0.915                                                                              22    0.85 1,220                                                                              Pluronic                                                                           226  2,760                                                          /6/  F-98 /6/  /6/                            Example IV                                                                            Polyethylene                                                                          0.965                                                                              19.5  "    1,060                                                                              Pluronic                                                                           166  2,600                                                               F-98 /6/  /6/                            __________________________________________________________________________

                                      TABLE B-2                                   __________________________________________________________________________                                             Rates                                                                               Rate of                               Dispersion Conditions             Resin Making                                                Im-     Resin                                                                              Addi-                                                                              Feed Rate                                                                           Dispersed                                             peller  Addition                                                                           tional                                                                             g     Material,                                                                           Yield                                                                              Average                                    Tip     Time,                                                                              Stirring                                                                           Liter ·                                                                    Liter ·                                                                    of   Particle                              Stirrer                                                                            Speed,                                                                            Temp.,                                                                            Min. Time 10 Min.                                                                             10 Min.                                                                             Powder,                                                                            Size,               Process of                                                                           Vessel and Stirring                                                                      rpm  ft/Min.                                                                           °C.                                                                        /12/ Min. /7/   /7,8/ %    Microns             __________________________________________________________________________    U.S. Pat. No.                                                                 3,422,049                                                                     Example I (A)                                                                        [(1-liter Parr Reactor,                                                                  8-10,000                                                                           4,200                                                                             200 8-10 None 1,100 1,100 100   3.65                      4-in. internal diameter                                                                       /11/                                                   Example IV                                                                           fitted with either a                                                                     8-10,000                                                                           4,200                                                                             200 0.5  None 19,000                                                                              19,000                                                                              86.8 6.5                        blade type (3 blades,                                                                         /11/                                                   Example VI                                                                           2-in. diameter) or                                                                        3,000                                                                             1,570                                                                             250 13   None   846   846 90.4 4.0                 Example V                                                                            two cured-tooth                                                                           1,000                                                                               524                                                                             200 7    None 1,450 1,450 92   5.5                        turbine-type discs                                                                            /11/                                                   Example X                                                                            (3-in. diameter) used                                                                    8-10,000                                                                           4,200                                                                             200 7    None 1,500 1,500 95   5.1                        in these experiments.]                                                                        /11/                                                   Example           8-10,000                                                                           4,200                                                                              270-                                                                             15   None   735   735 96.7 <10                 XIII                   /11/                                                                              210                                                Example XIV       8-10,000                                                                           4,200                                                                             200 7-10 None 1,100 1,100 /14/  2.56                                      /11/                                                   U.S. Pat. No.                                                                 3,432,493                                                                     Example 1                                                                            (3 Turbine type                                                                          /4/  515 207 6.0  None   445   445 High 8.9                 Example IV                                                                           rotors in a pressure                                                                     /4/  515 220 7.5  None   545   545 High  11                        vessel)                                                                __________________________________________________________________________     Footnotes for Tables A1, A2, B1 and B2                                        /1/ Decalin solution. Calculated from [η] = ηsp/C(1 + 0.28            ηsp), where sp is specfic viscosity as in U.S. Pat. No. 4,174,335.        /2/ Considerable scatter in successive values.                                /3/ Block copolymer of ethylene oxide and propylene oxide of molecular        weight of 13,500 and containing 20 percent by weight of propylene oxide       and 80 percent by weight of ethylene oxide.                                   /4/ Not disclosed.                                                            /5/ Block copolymer of ethylene oxide and propylene oxide of 16,250           molecular weight and containg 80 percent by weight of ethylene oxide and      20 percent by weight of propylene oxide.                                      /6/ Amounts of resin, dispersant and water were calculated from hourly        rates during a prolonged continuous run.                                      /7/ Units chosen to correspond to those of U.S. Pat. No. 4,174,335.           /8/ Includes time during which dispersion was being made and any              additional stirring time at dispersion temperature.                           /9/ No disclosure of geometry and size of impeller.                           /10/ Insufficient data to calculate; see /9/.                                 /11/ Calculated for minimum tip speed, i.e., 2in. impeller at lower rpm.      /12/ For this invention and U.S. Pat. No. 3,422,049, the time during whic     rapid stirring was applied: in this invention 15 minutes was taken as the     "normal" dispersion time although the period may range from 10 to 15          minutes; for U.S. Pat. No. 3,432,483, the residence time in the dispersio     reactor during continuous reaction; for U.S. Pat. No. 4,174,335, stated       resin addition time.                                                          /13/ Vinyl acetate content, 33 weight percent.                                /14/ Not determined, product used as film forming latex.                      /15/ Amounts in parenthesis calculated on basis of 150 g. total resin         charge of the present invention.                                         

At dispersion times from as low as 0.5 minutes to as high as 15 minutes(Table B-2), and at stirring speeds ranging from 1,000 rpm to as high as8,000-10,000 rpm, there is little difference in number average particlesize (Table B-2), which falls in the range of 2.6-11 microns for avariety of resins. Under the high resin addition rates of thepowder-producing process of U.S. Pat. No. 3,422,049 with Pluronicdispersants, addition rates that are characteristic of the presentinvention as well as stirring rates from 1,000 to 10,000 rpm (Table B-2)have little effect on particle size. Variations in the resin feed ratecorresponding to as little as 445 to as high as 19,000 grams ofdispersed material produced per liter of aqueous medium per 10 minuteperiod also failed to exert any remarkable effect on particle size. Infact, it is a disadvantage of the processes of U.S. Pat. Nos. 3,422,049and 3,432,483 that particle size is quite insensitive to changes invariables, whatever significance the high shear stirring specified inU.S. Pat. No. 4,174,335 may have for producing stable aqueousdispersions of ultrafine particles under conditions of slow addition ofa resin blend specified therein.

Accordingly, it has been concluded that in all high rate powderproduction processes as herein indicated, stirring beyond a minimumamount has comparatively little effect on particle size. Moreover, itappears likely that the stirring conditions given for the high rateprocesses shown in Table B-1 and B-2 are probably not greatly differentfrom those of U.S. Pat. No. 4,174,335, since the stirrer speeds are inthe same range, and this would apply to the present invention as well.Since the particle sizes of the present invention are considerablylarger than those disclosed in U.S. Pat. No. 4,174,335, the latter isnot suggestive of the particle sizes of the present invention.

The dispersions resulting from the above process are compositionscomprising a dispersion of an ionomer polymer-coated, normally solidsynthetic organic polymeric thermoplastic resin in water. Thedispersions may be utilized in preparing water-borne coatings for metal,glass, fabrics, paper and wood, alone or in combination with otherdispersions or latices; in paint formulations, and in polishformulations, etc. For some applications, it may be desirable to acidifythe aqueous resin dispersions herein prior to filtration such as by theaddition of small quantities of strong acid or a weak acid such asacetic acid, or to exchange the sodium ion with an ion of another metal,e.g., magnesium, calcium, barium, cadmium, zinc, aluminum, iron, cobalt,nickel, tin, etc.

To recover the powders of this invention from the resin dispersions, thetemperature of the dispersion may be lowered to below about 100° C., andthe resin separated from the aqueous phase in the form of discreteparticles by filtration, centrifugation, evaporation of the water, andthe like. It is a feature of this invention that the powder productcontains dispersing agent substantially retained on the surface of theresin particles. The ionomeric dispersing resin is substantiallyinsoluble in water and is not removed. Moreover, in the case of suchordinarily tacky resins as ethylene-vinyl ester copolymer, the resinswill be rendered non-tacky by being uniformly coated with a thin film ofionomer polymer.

Drying of the recovered finely-divided resins yields a free-flowingpowder of fine particle size and a particle size distribution that canbe controlled to within narrow limits by proper choice of suchoperational parameters as dispersion temperature, total resin solids,ratio of ionomer to thermoplastic resin, degree of neutralization of theionomer, and in particular how these variables relate to the initialcarboxylic acid content of the copolymer from which the ionomer is made,and the nature and composition of the termoplastic resin. Generally, allof the dispersed particles have diameters less than about 800 andgreater than about 10 microns. Especially preferred are particles ofnarrow size distribution wherein the number average particle size isless than about 150 microns, and more desirably, less than about 100microns, but not less than about 10 microns.

The finely-divided resins of this invention are superior in powder formfor static or fluidized dip coating, spraying, dusting, and flamespraying applications as well as for preparing stable dispersions inwater or some other medium for use in roller, dip, or spray coating. Therelatively high molecular weight resins of this invention also find usein the preparation of heat resistant coatings, in the preparation ofmolded or formed shapes by powder or slush molding techniques, and inthe preparation of foams in combination with conventional blowingagents.

In addition to the above-mentioned uses of the powder products of thisinvention, two special uses have discovered:

Thermoplastic Elastomers

When ethylene-vinyl acetate copolymers containing about 35 to 65,preferably 40 to 60, weight percent of vinyl acetate, are dispersed withabout 5 to about 40 parts and preferably 8-20 parts by weight of ionomerdispersing resin per 100 parts by weight of the copolymer under thecondition of this invention, and the recovered powder products aremolded into articles such as sheeting, hose, gasketing, O-rings, etc.,by conventional equipment and techniques, the articles exhibit theproperties of thermoplastic elastomers, e.g., they possess tensilestrengths considerably higher than that which would be expected for alinear relationship between the tensile strength of the ethylene-vinylacetate copolymer itself and the tensile strength of the ionomer. Forexample, the measured tensile strength of an ethylene-vinyl acetatecopolymer containing about 40 weight percent of vinyl acetate that wasused was about 1410 psi, whereas the measured tensile strength of theSurlyn 1555 was 2,610 psi. Compression molded sheets (Table XVIII) madefrom powders containing 10 and 20 parts by weight of Surlyn 1555 per 100parts by weight of the ethylene-vinyl acetate copolymer had tensiles of2,000 to 2,200 psi, respectively, whereas the interpolated values to beexpected for a linear relationship of tensile strength with compositionwould only be 1,510 to 1,600 psi, respectively. Hand in hand with thepositive deviation in tensile strength goes a corresponding decrease inmelt flow rate to as low as 0.59 and 0.42 g/10 min, respectively, ascompared to 1.40 g/10 min, for the original ethylene-vinyl acetatecopolymer and 0.59 for the Surlyn 1555. Solubility studies have shownthe powder samples to be completely soluble and therefore not gelled.Accordingly, these elastomeric compositions can be molded likethermoplastics but exhibit tensile properties that would be acceptablefor a peroxide-cured ethylene-vinyl acetate copolymer elastomer.

It has also been found that similar powder products made by dispersionand comprising 10 and 20 parts by weight of Surlyn 1555 in 100 parts byweight of low density polyethylene, when molded into sheets, exhibittensile strengths that are lower than the interpolated linear values,i.e., 1300 and 1420 psi, respectively, as compared to interpolatedvalues of 1500 and 1620 psi. Thus the system polyethylene-Surlyn 1555exhibits negative tensile deviations.

Simple mill-mixing of similar compositions of Surlyn 1555 andethylene-vinyl acetate and of Surlyn 1555 and low density polyethylenewill also yield materials respectively exhibiting positive and negativedeviations of tensile strength from linearity. However, the positivedeviations shown by the mill blends of Surlyn 1555 with ethylene-vinylacetate are about 100 to 300 psi less than those of the correspondingblends made by dispersion (Table XVIII). However, mill blends of Surlyn1555 with low density polyethylene show less negative deviation fromlinearity than dispersion blends, amounting to about 150 psi.

It is speculated that increased strength properties may be a consequenceof a type of intermolecular interaction between the polar groups of theethylene-vinyl acetate copolymer and Surlyn 1555, and that thisinteraction proceeds to a greater extent in the specimens derived fromthe powder process because more intimate mixing is possible than insimple mill-blending. It may also be that ionomer-encapsulated particlesmay persist, even into molded specimens, and that ionomer-ionomerinteractions may play a part. These speculations are offered merely byway of a possible explanation of the phenomena noted herein are notintended to limit the invention in any way.

Impact Modifier Powders

It is well-known in the art that ethylene-vinyl acetate copolymerscontaining about 40-50 weight percent of vinyl acetate are excellentimpact modifiers in rigid polyvinyl chloride. As ordinarily supplied,however, such copolymers are available as pellets which tend to adhereto each other because of their tacky nature. Since polyvinyl chloride issupplied as a powder with a particle size of about 100-150 microns, itis difficult to blend the pellets into it without imparting anundesirable heat history. Polyvinyl chloride formulators and processorsare becoming increasingly committed to powder blending technology andare requiring that ethylene-vinyl acetate copolymer impact modifiers beavailable as dry-blendable powders.

Dispersions of these tacky resins made with ethylene oxide-propyleneoxide block copolymer dispersing agents coalesce upon filtration and thedispersed material cannot be recovered as a powder. Heretofore, tackycopolymers such as the foregoing could only be recovered as dry powdersby dispersing them with alkali metal soaps and after dispersionchemically converting the soap to the free acid or to an alkaline earthmetal soap (U.S. Pat. No. 4,151,135). The fatty acid or alkaline earthmetal, e.g. calcium, soap thereof coats the tacky copolymer particlessufficiently for the latter to be recovered by filtration, dried, andapplied as dry-blendable impact modifier powders in rigid polyvinylchloride. Attempts to recover the dispersed material coated only withthe fatty acid in the alkali metal, e.g., sodium, soap form have beenunsuccessful. However, in the present invention, where an ionomericresin in the solium form is used as the dispersing agent, the powderproduct can readily be recovered by filtration and dried and evenresists considerable compaction. Surprisingly, it is not necessary toconvert the alkali metal, i.e., sodium form of the ionomer resin to thecorresponding acid or calcium form although at times this latterprocedure may be advantageous and is therefore within the scope of thisinvention. The ionomer dispersing resin thus appears to coat the outsideof the finely-divided, tacky, ethylene-vinyl acetate copolymerparticles, thus rendering them resistant to coalescence and permittingthem to be applied as dry powders.

Ethylene-vinyl acetate copolymer powders intended as dry-blendableimpact modifiers desirably have particle sizes in the range of about50-500 microns, with substantially no particles below 10 microns, indiameter. Ethylene-vinyl acetate powders such as these are not obtainedby the process of U.S. Pat. No. 4,174,335, which is directed to theproduction of stable latexes in which the particle size is typically nomore than 3 microns. The latter particles, if they could be recovered aspowders, would be entirely too fine for use as impact modifier powdersin rigid polyvinyl chloride because they would tend to segregate fromthe coarser polyvinyl chloride powder during handling due to the greatdisparity in particle size. In addition, they would have otherobjectionable features such as presenting an increased dust explosionhazard and would be in the respirable dust particle range (e.g., belowabout 10 microns).

The process of the present invention, however, readily lends itself tothe production, at high rates, of ionomer-coated ethylene-vinyl acetatecopolymer powders suitable for dry blending into rigid polyvinylchloride powder formulations. The particle size and particle sizedistribution can be substantially controlled, e.g., by suitableadjustment of the ratio of ionomer dispersing resin to ethylene-vinylacetate copolymer or by blending the resins before dispersion andthereafter suitably selecting the dispersion temperature or extendingthe hold time at dispersion temperature.

Ethylene-vinyl acetate copolymer powder made with, and containing both10 and 20 parts by weight of ionomer resin per 100 parts by weightcopolymer, are both dry blendable with polyvinyl chloride and impartexcellent impact resistance thereto. Aging properties (weatherometer) ofrigid polyvinyl chloride formulations made with the powders as impactmodifiers compare favorably with those made with pellets of the parentethylene-vinyl acetate copolymer.

The following examples will further illustrate this invention withoutlimitations. All parts are by weight unless otherwise indicated.

Resins

Resins used in the examples were characterized by their flow ratesdetermined according to ASTM D-1238. "Melt Index" hereinafter refers toa melt flow rate determined according to Condition E thereof, i.e., witha 2,160 g weight at 190° C. Unless otherwise specified, the term "meltflow rate" hereinafter means melt flow rate determined according toCondition B thereof, with a 2,160 g weight at 125° C.

Intrinsic viscosity [η] was also employed to characterize the resins andwas calculated as in U.S. Pat. No. 4,174,335 from the equation:

    [η]=η.sub.sp /C(1+0.28η.sub.sp),

where η_(sp) is the specific viscosity of the resin measured in decalinsolution at a concentration (C) of 0.1 g/100 ml.

Thermoplastic Resins

Petrothene NA 202--U.S. Industrial Chemicals Co.

Petrothene NA 202 is a low density polyethylene supplied in the form ofpellets. It has a melt index of 22 g/10 min., a density of 0.915 g/cc,and an intrinsic viscosity 0.85.

Petrothene LS-630--U.S. Industrial Chemicals Co.

Petrothene LS-630 is a high density polyethylene; melt index 28 g/10min.; density, 0.962 g/cc; intrinsic viscosity 1.0.

Ethylene-Vinyl Acetate (EVA) Copolymer (Vynathene EY 901)--U.S.Industrial Chemicals Co.

Vynathene EY 901 is supplied as pellets and was employed as a modelethylene-vinyl acetate copolymer. It contains about 40 weight percent(nominal) of vinyl acetate. It has a melt flow rate of 0.5-1.5 g/10 min.and a density of 0.962 g/cc.

Dispersing Resins

Ethylene-Acrylic Acid (EAA) Copolymers--Dow Chemical Co.

Three EAA coppolymers trade-named "Dow Polyethylene 435, 455, and 459"were tested as dispersing resins, after conversion with sodium hydroxideto the sodium ionomer form in situ during dispersion. Properties of theEAA copolymers were as follows:

    ______________________________________                                               Nominal Values Provided                                                                         Measured                                                    by Supplier       Values                                                                           Acrylic                                                                              Acrylic                                                      Melt      Acid   Acid                                       EAA      Density  Index     Content                                                                              Content                                                                              Acid                                Copolymer                                                                              g/cc     g/10 Min. Wt. %  Wt. %  No.                                 ______________________________________                                        Dow PE 435                                                                             0.925    11.0      3.5    3.0    23                                  Dow PE 455                                                                             0.932    5.5       8      5.4    42                                  Dow PE 459                                                                             0.932    9.0       8      5.0    39                                  ______________________________________                                    

Calculations in this invention are based on measured analtyical valuesobtained for EAA copolymers.

Surlyn 1555--E. I. duPont de Nemours and Co.

Surlyn 1555 is the sodium form of a partially-neutralizedethylene-methacrylic acid copolymer, available as pellets. It istherefore a terpolymer of ethylene, methacrylic acid and sodiummethacrylate. Duplicate analysis by atomic absorption showed thepresence of 1.02, 1.04 weight percent sodium equivalent to 4.84 weightpercent (average) of sodium methacrylate. Titration with standardmethanolic KOH at about 50°-60° C. of Suryln 1555 in 2:1decalin-dimethylacetamide solution gave an unneutralized methacrylicacid content of 5.93 weight percent. Accordingly, the Surlyn 1555 usedhere contained a total of 9.8 weight percent of methacrylic acid unitsbefore conversion to ionomer, corresponding to an initial acid number of64. According to the above analysis the ionomer was 39.5% neutralized,as supplied. All calculations in the invention are based on theforegoing analysis.

The Surlyn 1555 used in the examples had a melt index of 10 g/10 min.and a density of 0.945 g/cc. Its melt flow rate was 0.59 g/10 min. andits intrinsic viscosity, 0.31, measured in 2:1 decalin-dimethylacetamide solution.

Dispersion Reactor

The dispersion experiments described hereinafter in the examples wereperformed in a one-liter Parr pressure reactor (Parr Instrument Company,Moline, Ill.). The reactor (4-inch internal diameter) was equipped witha thermocouple well, blow-out disc assembly, and a mechanical stirrer.The stirrer was driven by a 1-horsepower electrical motor (DaytonElectric Manufacturing Co., Chicago, Ill.) attached to a drill press(Craftman 150, Sears, Roebuck & Co.). The reactor was heatedelectrically with an external heating jacket. The impeller consisted oftwo 3-inch diameter toothed discs mounted about 1-inch apart on thestirrer shaft.

General Dispersion Procedure

At the start of a dispersion experiment the aqueous dispersion mediumwas charged to the open rector. Deionized water was used throughout and,unless otherwise specified, the volume added was 450 ml. In manyexperiments, sodium hydroxide solutions in deionized water replaceddeionized water as the aqueous dispersion medium.

In some experiments, the resin to be dispersed and the dispersing resinwere each added separately as pellets. In other experiments, the tworesins were blended before dispersion by milling them together in atwo-roll rubber mill for 5 minutes at 235° F. (113° C.) or as otherwisespecified. Thereafter the blends were cut into small pieces for addingto the open dispersion reactor.

The reactor was then closed, connected to the drill press stirrerassembly and heated to the dispersion temperature with the stirrerturned off. To reach 200° C., the most commonly used dispersiontemperature, a period of about 30 minutes were required. Immediatelyupon reaching the dispersion temperature, the stirrer was started at3,700 rpm, the heat to the heating jacket was turned off and granulateddry ice was packed over the top of the reactor to hasten cooling. Withcontinuous stirring at 3,700 rpm, the reactor was cooled at about 100°C. At this point the stirring was discontinued. Stirring speed wasmonitored frequently during this period with a Strobotac Type 1531-A(General Radio Co., Concord, Mass.). The total period from the time thestirring was started to the time the temperature reached 100° C. and thereactor could be safely opened, amounted to 10 to 15 minutes. This 10 to15 minute dispersion time is referred to hereinafter as the "normal"dispersion time. In this procedure the temperature at which stirring wasstarted is referred to hereinafter as the "dispersion temperature". Insome experiments, the dispersion period was extended by applying longerhold times, up to 20 minutes, at the temperature of dispersion.Thereafter the reactor was cooled as described above, to 100° C., over10 to 15 minutes.

After cooling to 100° C., the reactor was opened and the dispersion waspromptly removed. The dispersed matter was suction filtered; washed, ifdesired, and dried. Recovery as powder was substantially 100%. Afterdrying, the powder was screened to determine particle size distribution.In most instances where substantial fractions having diameters <53microns were formed on screen analysis, a specimen of the total productwas examined under an optical microscope to determine how many particlesper 100 particles had diameters below 10 microns. In general the numberwas small, i.e. 0-6/100.

In-Situ Neutralization of Dispersing Resins

In experiments in which Surlyn 1555 was the dispersing resin, sodiumhydroxide was often added to the dispersion medium to neutralize some orall of the residual unneutralized methacrylic acid units present. Insome experiments, amounts of sodium hydroxide in excess ofneutralization of the methacrylic acid units were added.

In the tables hereinafter, the amount of sodium hydroxide added is givenin terms of weight percent concentration in the aqueous medium. Fromthis concentration and the total volume of aqueous medium, calculationswere made of the ratio of equivalents of sodium hydroxide tounneutralized methacrylic acid units (NaOH/--COOH) in the Surlyn 1555 asadded. Since Surlyn 1555 also contains sodium methacrylate units, theratio of total sodium ion present during dispersion to total methacrylicacid units present, neutralized and unneutralized, was also calculated(Ma+/MAA). This ratio relates the degree of neutralization plus anyamount of excess alkali to total carboxylic acid amount of thedispersing resin. In experiments where Dow ethylene-acrylic acidcopolymers were used as dispersing resins, sufficient alkali was addedto the aqueous medium to give the stated degrees of neutralization.

EXAMPLE 1

In accordance with the general dispersion procedure above, Petrothene NA202 low density polyethylene was dispersed with three different Dowethylene acrylic acid copolymers (Dow polyethylenes No. 435, 455, and459), these copolymer resins as well as the Petrothene NA 202 beingadded separately as pellets in each experiment, and with sufficientsodium hydroxide being added to the aqueous medium for halfneutralization in situ of the copolymers during dispersion. The powderproducts recovered are described in Table I along with the correspondingdispersion conditions.

Particle sizes are relatively coarse, with little material below 53microns being present. Particle size distributions are rather broad.Increasing the acrylic acid content of the ionomer precursor from 3%(Dow PE 435) to 5-5.5% (Dow PE 455 and 459) favors finer particle sizeat least at the lower ionomer/polyethylene ratio. The effect ofincreasing ionomer/polyethylene ratio is variable.

                                      TABLE I                                     __________________________________________________________________________    POWDERS MADE BY DISPERSING PETROTHENE NA 202 LOW DENSITY POLYETHYLENE         WITH                                                                          DOW ETHYLENE-ACRYLIC ACID COPOLYMERS IN WATER CONTAINING                      SUFFICIENT NaOH FOR HALF NEUTRALIZATION.                                      RESINS INTRODUCED SEPARATELY AS PELLETS                                                           Aqueous Medium                                                                         450 ml.                                                              Dispersion Temp.                                                                       200° C.                                                       Dispersion Time                                                                        Normal                                                    EAA Copolymer       Particle Size Distribution in Weight                                          Percent                                          Petrothene        Wt. %                                                                              Melt  per Particle Size Fraction (Microns)             Exp.                                                                             NA 202,        Acrylic                                                                            Index,   53-                                                                              106-                                                                             149-                                                                             250-                                                                             420-                                                                             600-                           No.                                                                              g.    Name   g.                                                                              Acid g/10 Min.                                                                           <53                                                                              106                                                                              149                                                                              250                                                                              420                                                                              600                                                                              850                                                                              >850                        __________________________________________________________________________    1  136   Dow PE 435                                                                           14                                                                              3.0  11    ←                                                                           ←                                                                           Marginal Dispersion                                                                       →                                                                         →                    2  125   "      25                                                                              3.0  11    0.9                                                                              5.3                                                                              7.1                                                                              24.3                                                                             29.6                                                                             16.0                                                                             11.7                                                                             4.5                         3   75   "      75                                                                              3.0  11    2.7                                                                              14.1                                                                             10.5                                                                             22.6                                                                             27.8                                                                             11.6                                                                             5.1                                                                              5.5                         4  136   Dow PE 455                                                                           14                                                                              5.4  5.5   11.4                                                                             30.0                                                                             18.5                                                                             20.5                                                                             12.7                                                                             4.1                                                                              1.5                                                                              1.3                         5  125   "      25                                                                              5.4  5.5   8.5                                                                              21.9                                                                             13.5                                                                             21.2                                                                             13.5                                                                             8.8                                                                              5.6                                                                              7.0                         6   75   "      75                                                                              5.4  5.5   11.6                                                                             19.2                                                                             9.6                                                                              23.8                                                                             15.8                                                                             5.8                                                                              3.8                                                                              10.0                        7  136   Dow PE 459                                                                           14                                                                              5.0  9.0   9.1                                                                              29.4                                                                             14.3                                                                             16.2                                                                             10.7                                                                             5.2                                                                              1.1                                                                              13.9                        8  125   "      25                                                                              5.0  9.0   11.7                                                                             31.2                                                                             17.0                                                                             18.1                                                                             10.3                                                                             6.0                                                                              2.4                                                                              3.2                         9   75   "      75                                                                              5.0  9.0   3.0                                                                              7.3                                                                              6.5                                                                              18.2                                                                             35.5                                                                             10.2                                                                             5.0                                                                              14.3                        __________________________________________________________________________

EXAMPLE 2

In accordance with the general dispersion procedure, Petrothene NA 202low density polyethylene was dispersed with Dow Polyethylene No. 455 inone series of experiments and Dow Polyethylene No. 459 in another seriesof experiments. In each experiment the Petrothene NA 202 and the Dowethylene-acrylic acid copolymers were introduced into the dispersionvessel separately, as pellets, and enough sodium hydroxide was added tothe water to neutralize half of the carboxyl groups of the Dowcopolymer. In each series dispersions were made at two differenttemperatures: 200° and 250° C. The results of the experiments appear inTable II.

The effect of going to a 250° C. dispersion temperature was to narrowthe particle size distribution in the intermediate particle size rangeat the expense of the finer particle size fractions. Under theconditions employed, judicious adjustment of the dispersion temperaturecan thus be used to achieve a degree of control over particle size.

                                      TABLE II                                    __________________________________________________________________________    POWDERS MADE BY DISPERSING PETROTHENE NA 202 LOW DENSITY POLYETHYLENE         WITH                                                                          DOW ETHYLENE-ACRYLIC ACID COPOLYMERS IN WATER CONTAINING                      NaOH SUFFICIENT FOR HALF NEUTRALIZATION.                                      RESINS INTRODUCED SEPARATELY AS PELLETS. DISPERSIONS AT 200 and               250° C.                                                                                        Aqueous Medium                                                                         450 ml.                                                              Time     Normal                                       Resins                                                                                  Dispersant             Dis- Particle Size Distribution in                                                 Weight Percent                          Petrothene       Melt  Acrylic   persion                                                                            per Particle Size Fraction                                                    (Microns)                               Exp.                                                                             NA 202        Index Acid, Amt.,                                                                             Temp.   53-                                                                              106-                                                                             149-                                                                             250-                                                                             420-                                                                             600-                  No.                                                                              g.     Name   g/10 Min.                                                                           Wt. % g.  °C.                                                                         <53                                                                              106                                                                              149                                                                              250                                                                              420                                                                              600                                                                              850                                                                              >850               __________________________________________________________________________    1  136    Dow PE 459                                                                           9.0   5.0   14  200  9.1                                                                              29.4                                                                             14.3                                                                             16.2                                                                             10.7                                                                             5.2                                                                              1.1                                                                              13.9               2  136    Dow PE 459                                                                           9.0   5.0   14  250  3.2                                                                              6.8                                                                              12.4                                                                             22.2                                                                             34.4                                                                             10.2                                                                             5.4                                                                              5.4                3  136    Dow PE 455                                                                           5.5   5.4   14  200  11.4                                                                             30.0                                                                             18.5                                                                             20.5                                                                             12.7                                                                             4.1                                                                              2.8                                                                              --                 4  136    Dow PE 455                                                                           5.5   5.4   14  250  1.3                                                                              1.7                                                                              4.1                                                                              39.4                                                                             49.1                                                                             3.0                                                                              1.3                                                                              5.0                5  125    Dow PE 455                                                                           5.5   5.4   25  200  9.1                                                                              23.6                                                                             14.5                                                                             22.8                                                                             14.5                                                                             9.5                                                                              6.0                                                                              7.0                6  125    Dow PE 455                                                                           5.5   5.4   25  250  3.5                                                                              8.1                                                                              8.1                                                                              23.1                                                                             29.1                                                                             15.0                                                                             1.9                                                                              11.1               __________________________________________________________________________

EXAMPLE 3

As described in the general dispersion procedure, Petrothene NA 202 lowdensity polyethylene was dispersed with Dow Polyethylene No. 455ethylene acrylic acid copolymer, neutralized to different degrees insitu during dispersion, both resins being added separately as pellets.Table III summarizes the results of these experiments.

As the degree of neutralization approaches completion, the particle sizedistribution of the powder product narrows and shifts to smallerparticle sizes. From this it is evident that degree of neutralization ofthe ionomeric dispersing resin is another parameter than can be used toadjust the particle size and particle size distribution of the powderproducts.

                                      TABLE III                                   __________________________________________________________________________    Powders Made by Dispersing Petrothene NA 202 Low Density                      Polyethylene with Dow Polyethylene 455 Ethylene-Acrylic Acid                  Copolymer Neutralized to Different Degrees in situ During Dispersion.         Resins Introduced Separately as Pellets                                                  Aqueous Medium                                                                          450 ml                                                              Petrothene NA 202                                                                       136 g                                                               Dow PE 455                                                                               14 g                                                               Dispersion Temp.                                                                        200° C.                                                      Dispersion Time                                                                         Normal                                                   NaOH        Particle Size Distribution in Weight Percent                             NaOH--                                                                             per Particle Size Fraction (Microns)                              Exp.                                                                             g.  COOH,   53-                                                                              106-                                                                             149-                                                                             250-                                                                             420-                                                                             600-                                            No.                                                                              Added                                                                             Molar                                                                              <53                                                                              106                                                                              149                                                                              250                                                                              420                                                                              600                                                                              850                                                                              >850                                         __________________________________________________________________________    1  0.125                                                                             0.30 3.3                                                                              12.1                                                                             11.4                                                                             28.1                                                                             24.2                                                                             13.1                                                                             5.9                                                                              1.8                                          2  0.250                                                                             0.60 8.9                                                                              31.4                                                                             16.4                                                                             23.7                                                                             12.4                                                                             3.7                                                                              0.9                                                                              2.5                                          3  0.375                                                                             0.89 8.9                                                                              29.2                                                                             22.0                                                                             20.5                                                                             8.7                                                                              5.7                                                                              2.2                                                                              2.7                                          __________________________________________________________________________

EXAMPLE 4

In the dispersion reactor, and in accordance with the general dispersionprocedure described above, a series of three experiments were performedin which Petrothene NA 202 low density polyethylene (136 g, 125 g, and100 g) in the form of pellets was charged to the reactor along withSurlyn 1555 (14 g, 25 g, and 50 g), also in the pellet form, and with450 ml deionized water in each experiment. Experimental data aretabulated in Table IV. Dispersion times in Experiments 1, 2 and 3 were12 minutes, 51 seconds; 12 minutes; and 15 minutes, respectively. It isapparent that as the ratio of Surlyn 1555 ionomeric resin topolyethylene increases, the particle size distribution of the powdernarrows and shifts to particle sizes below 53 microns. Microscopicexamination of the 53-micron fractions shows, however, that no more thanabout 4 per 100 particles have a diameter of 5-10 microns; the remainderare larger. The Surlyn 1555 used in the experiment contained 9.8 weightpercent methacrylic acid (total) and was 39.5% neutralized. Comparisonwith Example 1 shows that much finer polyethylene particles are producedwith Surlyn 1555 than with the Dow ethylene-acrylic acid-based ionomerswhich contain 5-5.5% acrylic acid. Carboxylic acid content of theionomer precursor thus represents another parameter for controllingparticle size.

                  TABLE IV                                                        ______________________________________                                        POWDERS MADE BY DISPERSING                                                    PETROTHENE NA 202 LOW DENSITY                                                 POLYETHYLENE IN WATER WITH SURLYN 1555                                        RESINS INTRODUCED SEPARATELY AS PELLETS                                       Aqueous Medium        450 ml                                                  Dispersion Temp.      200 ° C.                                         Dispersion Time       Normal                                                  Resins        Particle                                                        Petro-            Size Distribution in Wt. Percent                            thene     Surlyn  per Particle Size Fraction (Microns)                        Exp. NA 202,  1555,        53-  106- 149- 250-                                No.  g        g       <53  106  149  250  420  >420                           ______________________________________                                        1    136      14      31.6.sup.1                                                                         31.4 11.8 15.9 8.4  0.8                            2    125      25      69.3.sup.2                                                                         22.3 4.4  3.3  0.7  Trace                          3    100      50      73.8.sup.3                                                                         18.8 3.4  3.1  0.9  Trace                          ______________________________________                                         .sup.1 Microscopic examination showed at most 3-4 particles per 100 were      of 5-10 microns in diameter; most were 10-100 microns in diameter             (examination made on total powder).                                           .sup.2 2-3 particles of 5-10 microns diameter per 100 particles; most wer     20-100 micron particles (examination on total powder).                        .sup.3 About 1 particle per 100 was 5-10 microns in diameter; most were       20-100 micron particles (examination on total powder).                   

EXAMPLE 5

Experiment No. 1 of Table IV was repeated exactly, except that stirringat 3,700 rpm was stopped after 7 minutes in the cooling period insteadof at the end of the 12 minute, 51 second period when the temperaturehad reached 100° C. in Experiment No. 1 of Table IV. The stirrer wasallowed to turn only slowly during the remaining minutes of the coolingperiod. Screen analyses of the powder product and that of Experiment No.1 of Table IV are compared in Table V. The analyses do not differsignificantly. Thus it is evident that the so-called 10 to 15-minute"normal" dispersion time can be reduced to at least 7 minutes, withoutproducing a significant change in particle size.

                  TABLE V                                                         ______________________________________                                        POWDERS MADE BY                                                               DISPERSING PETROTHENE NA 202                                                  LOW DENSITY POLYETHYLENE                                                      IN WATER WITH SURLYN 1555                                                     RESINS INTRODUCED SEPARATELY AS PELLETS                                       REDUCTION OF DISPERSION TIME                                                  Aqueous Medium         450 ml.                                                Petrothene NA 202      136 g                                                  Surlyn 1555            14 g                                                   Dispersion Temp.       200 C.                                                             Particle Size Distribution in                                                 Weight Percent per Particle Size                                              Fraction (Microns)                                                Exp. Dispersion          53-  106  149- 250-                                  No.  Time, Min.   <53.sup.1                                                                            106  149  250  420  >420                             ______________________________________                                        1    12 min., 51 sec.                                                                           31.6   31.4 11.8 15.9 8.4  0.8                              2    7            30.7   31.6 18.6 10.4 7.8  7.8                              ______________________________________                                         .sup.1 On microscopic examination about 1 particle per 100 was 5-10           microns in diameter; most were 20-100 micron particles (examination on        total powder).                                                           

EXAMPLE 6

Two additional experiments were performed under the dispersionconditions of Example 4, except that the total resin solids wasincreased to 33 and 50%. In Table VI the results of these experimentsare compared with those obtained at 25%. It is evident that increasingtotal solids during the dispersion process also favors narrower particlesize distributions and finer particles. Therefore, regulation of totalsolids provides a means of controlling particle size.

                                      TABLE VI                                    __________________________________________________________________________    POWDERS MADE BY DISPERSING PETROTHENE NA 202 LOW                              DENSITY POLYETHYLENE IN WATER WITH SURLYN 1555. RESINS                        INTRODUCED SEPARATELY AS                                                      PELLETS. EFFECT OF TOTAL SOLIDS.                                                           Dispersion Temp.                                                                       200° C.                                                       Dispersion Time                                                                        Normal                                                                       Particle Size Distribution in Weight                                      Total                                                                             Percent per Particle Size Fraction                       Petrothene                                                                             Surlyn  Resin                                                                             (Microns)                                                Exp.                                                                             NA 202,                                                                             1555,                                                                             Water,                                                                            Solids,                                                                              53-                                                                              106-                                                                             149-                                                                             250-                                         No.                                                                              g.    g.  ml. Wt. %                                                                             <53                                                                              106                                                                              149                                                                              250                                                                              420                                                                              >420                                      __________________________________________________________________________    1  136   14  450 25  31.6.sup.1                                                                       31.4                                                                             11.8                                                                             15.9                                                                             8.4                                                                              0.8                                       2  182   18  400 33  41.3.sup.2                                                                       27.2                                                                             12.5                                                                             11.4                                                                             6.5                                                                              1.1                                       3  273   27  300 50  63.5                                                                             24.1                                                                              6.0                                                                              4.8                                                                             1.2                                                                              0.4                                       __________________________________________________________________________     .sup.1 Upon microscopic examination about 1 particle per 100 was 5-10         microns in diameter; most were 20-100 micron particles (examination on        total powder).                                                                .sup.2 No particles out of 100 examined below 10 microns in diameter          (examination on total powder).                                           

EXAMPLE 7

Following the general dispersion procedure, Petrothene LS 630 highdensity polyethylene was dispersed in water at 200° C. with Surlyn 1555.Table VII contains the results of these experiments.

As in Example 4, it is seen that increasing the relative amount ofSurlyn 1555 employed for the dispersion leads to a narrowing of particlesize distribution in the finest particle size range.

                  TABLE VII                                                       ______________________________________                                        Powders Made by Dispersing Petrothene LS 630                                  High Density Polyethylene in Water with Surlyn 1555.                          Resins Introduced Separately as Pellets                                       Water                 450 ml                                                  Dispersion Temp.      200° C.                                          Dispersion Time       Normal                                                  Resins                                                                        Petro-           Particle Size                                                thene            Distribution in Weight Percent                               LS-      Surlyn  per Particle Size Fraction (Microns)                         Exp. 630,    1555,         53-  106- 149- 250-                                No.  g.      g.      <53   106  149  250  420  >420                           ______________________________________                                        1    136     14      Trace  1.0 0.8  7.6  21.8 68.8                           2    125     25      16.6  26.9 10.5 10.5 4.7  0.8                            3    100     50      70.9.sup.1                                                                          16.1 4.1  4.8  2.2  1.9                            ______________________________________                                         .sup.1 Microscopic examination revealed no particles less than 10 microns     in diameter (examination made on total powder).                          

EXAMPLE 8

In a series of three experiments performed according to the generaldispersion procedure, Vynathene EY 901, and ethylene-vinyl acetatecopolymer containing about 40 weight percent of vinyl acetate (136 g,125 g, and 100 g) was dispersed with Surlyn 1555 (14 g, 25 g, and 50 g)respectively, in 450 ml of deionized water in each experiment. White,free-flowing resin powders wre recovered in high yields in eachexperiment. Table VIII summarizes the experimental details, includingthe screen analysis of the powder products.

As in the dispersion of polyethylene under similar conditions (Example 4and 7), an increase in the ratio of Surlyn 1555 to Vynathene EY 901leads to a narrowing of the particle size distributions, with a shift tofiner particle sizes. The powders have good resistance to compactionunder the pressure generated by their own weight. For example, they donot coalesce under a pressure of 1 psi applied at 39°-40° C. for 24hours, however, they are not as compaction-resistant as the calciumstearate-coated powders of U.S. Pat. No. 4,151,135.

It is surprising that the powders of this example, coated with Surlyn1555, an ionomer in the sodium-ion form, can be recovered as drypowders. Comparabe powders coated with sodium stearate, for example,cannot be so recovered (U.S. Pat. No. 4,151,135).

                  TABLE VIII                                                      ______________________________________                                        Powders Made by Dispersing Vynathene EY 901                                   Ethylene-Vinyl Acetate Copolymer in Water with Surlyn 1555.                   Resins Introduced Separately as Pellets                                       Water                 450 ml                                                  Dispersion Temp.      200° C.                                          Dispersion Time       Normal                                                  Resins                                                                        Vyna-            Particle Size                                                thene            Distribution in Weight Percent                               EY       Surlyn  per Particle Size Fraction (Microns)                         Exp. 901,    1555,         53-  106- 149- 250-                                No.  g.      g.      <53   106  149  250  420  >420                           ______________________________________                                        1    136     14      Trace  5.2 10.7 25.9 16.3 41.9                           2    125     25      35.0.sup.1                                                                          22.8 12.3 12.7 11.9 5.2                            3    100     50      40.7  25.7 12.9  9.5  7.8 3.3                            ______________________________________                                         .sup.1 Microscopic examination showed no particles out of 100 with a          diameter of 10 microns or less (examination made on total powder).       

EXAMPLE 9

Petrothene NA 202 low density polyethylene was dispersed with DowPolyethylene 459 ethylene-acrylic acid copolymer in a series ofexperiments in which the effect of blending the two resins beforedispersion was compared with results obtained when the two resins wereadded to the reactor separately as pellets. The results are shown inTable IX.

At the degree of neutralization employed (0.65), the blended resins gavenarrower particle size distributions of finer particles. Accordingly,blending before dispersion can be employed to control particle size andparticle size distribution.

                                      TABLE IX                                    __________________________________________________________________________    POWDERS MADE BY DISPERSING PETROTHENE NA 202 LOW DENSITY POLYETHYLENE         WITH                                                                          DOW POLYETHYLENE 459 ETHYLENE-ACRYLIC ACID COPOLYMER.                         COMPARISON OF BLENDING RESINS BEFORE DISPERSION WITH SEPARATE ADDITION                       Aqueous Medium                                                                           450 ml.                                                            Dispersion Temp.                                                                         200° C.                                                     Dispersion Time                                                                          Normal                                              Resins                                                                                      Mill  NaOH         Particle Size Distribution in Weight                                          Percent                                      Petrothrene                                                                            Dow PE                                                                             Blended      NaOH  per Particle Size Fraction (Microns)         Exp.                                                                             NA 202                                                                              459  Before                                                                              Conc., --COOH,  53-                                                                              106-                                                                             149-                                                                             250-                                                                             420-                          No.                                                                              g.    g.   Dispersion.sup.1                                                                    Wt. %                                                                             g. Molar <53                                                                              106                                                                              149                                                                              250                                                                              420                                                                              600   >600                    __________________________________________________________________________    1  136   14   No    0.055                                                                             0.25                                                                             0.64  9.1                                                                              29.4                                                                             14.3                                                                             16.2                                                                             10.7                                                                             5.2   13.9                    2  136   14   Yes   0.055                                                                             0.25                                                                             0.64  7.1                                                                              40.4                                                                             24.1                                                                             15.0                                                                             5.0                                                                              8.4(>420)                                                                           --                      3  125   25   No    0.1 0.45                                                                             0.65  11.7                                                                             31.2                                                                             17.0                                                                             18.1                                                                             10.3                                                                             6.0    3.2                    4  125   25   Yes   0.1 0.45                                                                             0.65  28.9                                                                             38.4                                                                             15.3                                                                             11.4                                                                             4.1                                                                              1.8(>420)                                                                           --                      __________________________________________________________________________     .sup.1 5 minutes at 113° C.                                       

EXAMPLE 10

This example compares the relative effects of blending resins beforedispersion with separate addition of the resins in the production ofpowder products by dispersing Vynathene EY 901 ethylene-vinyl acetatecopolymer with Dow Polyethylene 459 ethylene-acrylic acid copolymerneutralized approximately 65% in situ during dispersion. A series offour experiments were performed, following the general dispersionprocedure described hereinabove. Results are summarized in Table X.

Blending of the two resins (5 minutes at 113° C. on a two-roll mill) isseen to shift the particle size distribution to finer particle sizes, ascompared to separate addition of the pellets. However, as compared topowders made in dispersing low density polyethylene with this sameethylene-acrylic acid based ionomer (Example 9, Table IX), particlesizes are coarser and the effect on particle size distribution is lessclear-cut.

                                      TABLE X                                     __________________________________________________________________________    POWDERS MADE BY DISPERSING VYNATHENE EY 901 ETHYLENE-VINYL ACETATE            COPOLYMER                                                                     WITH DOW PE 459 ETHYLENE-ACRYLIC ACID COPOLYMER                               APPROXIMATELY 65% NEUTRALIZED IN SITU DURING DISPERSION.                      COMPARISON OF BLENDING RESINS BEFORE DISPERSIONS WITH SEPARATE ADDITION                            Aqueous Medium                                                                          450 ml                                                              Dispersion Temp.                                                                        200° C.                                                      Dispersion Time                                                                         Normal                                         Resins                                                                                      Resins                                                                              NaOH         Particle Size Distribution in Weight                                          Percent                                      Vynathene                                                                              Dow PE                                                                             Blended                                                                             Conc., NaOH  per Particle Size Fraction (Microns)         Exp.                                                                             EY 901,                                                                             459, before                                                                              Wt.    --COOH,   53-                                                                              106-                                                                             149-                                                                             250-                                                                             420-                         No.                                                                              g.    g.   Dispersion                                                                          %   g. Molar <53 106                                                                              149                                                                              250                                                                              420                                                                              600                                                                              >600                      __________________________________________________________________________    1  136   14   No    0.055                                                                             0.25                                                                             0.64  0.6 2.2                                                                              3.8                                                                              9.3                                                                              12.6                                                                             6.8                                                                              64.7                      2  136   14   Yes   0.055                                                                             0.25                                                                             0.64  6.3 21.4                                                                             15.0                                                                             17.3                                                                             16.3                                                                             9.8                                                                              14.7                      3  125   25   No    0.1 0.45                                                                             0.65  1.0 5.8                                                                              5.5                                                                              20.1                                                                             14.5                                                                             10.2                                                                             42.8                      4  125   25   Yes   0.1 0.45                                                                             0.65  Trace                                                                             6.0                                                                              6.4                                                                              19.7                                                                             16.1                                                                             25.6                                                                             26.1                      __________________________________________________________________________

EXAMPLE 11

Two experiments were preformed as described in the general dispersionprocedure described hereinabove, in which Vynathene EY 901ethylene-vinyl acetate copolymer was dispersed with Dow Polyethylene 459ethylene-acrylic acid copolymer approximately 65% neutralized in situduring dispersion. The two resins were melt-blended before dispersing.In one experiment, the normal dispersion time was employed, in the otherexperiment stirring at 3,700 rpm was maintained over an additional holdtime of 20 minutes at 200° C. (Table XI).

The longer hold time narrowed the particle size distribution, with 83%of the product particles falling in the range of 149-600 microns.Similar narrowing of particle size distribution with increased hold timewas observed when Vynathene EY 901 was dispersed with Surlyn 1555(Example 16). In neither example, however, were there any significantincrease in the finest fraction (<53 microns) at longer hold times.

                  TABLE XI                                                        ______________________________________                                        POWDERS MADE BY DISPERSING BLENDS OF                                          VYNATHENE EY 901 WITH DOW POLYETHYLENE                                        459 ETHYLENE-ACRYLIC ACID COPOLYMER                                           65% NEUTRALIZED IN SITU DURING                                                DISPERSIONS EFFECT OF DISPERSION TIME.                                        Aqueous Medium         450 ml                                                 Vynathene EY 901       136 g                                                  Dow PE 459             14 g                                                   NaOH/--COOH            0.65                                                   Dispersion Temp.       200° C.                                                    Particle Size Distribution in Weight Percent                       Dispersion per Particle Size Fraction (Microns)                               Exp. Time             53-  106- 149- 250- 420-                                No.  Min.      <53    106  149  250  420  600  >600                           ______________________________________                                        1    Normal    5.3    21.4 15.0 17.3 16.3  9.8 14.7                           2    20        0.3     3.1  5.0 23.4 43.4 16.3  8.4                           ______________________________________                                    

EXAMPLE 12

Two blends of the same polyethylene and Surlyn 1555 used in Example 4were made on a two-roll mill to provide sufficient starting material fora number of experiments. Surlyn 1555 was blended at 10 (Blend B-1) and20 (Blend B-2) parts by weight per 100 parts by weight of polyethylene.Two blending was done at 113° C. for a period of 5 minutes. Thereafterthe sheeted blends were cut into small pieces suitable for introductioninto the dispersion reactor.

In two separate experiments, 150 g of each blend was subjected todispersion as described in Example 4 in 450 ml of deionized water at200° C. and 3700 rpm. No dispersion was recovered from Blend B-1 and 90%of the product of Blend B-2 was above 420 microns in particle size. In athird experiment Blend B-2 was stirred at 200° C. for 20 minutes beforecooling. Slightly better, but still unacceptable, powder products wererecovered. Table XII summarizes the results.

From Table XII it is evident that blends of Surlyn 1555 and polyethylenecannot be dispersed satisfactorily in water at 200° C. after as much as20 minutes longer hold time. These unexpected results reveal thatblending polyethylene with the dispersing resin already in the ionomericform is not equivalent to introducing the polyethylene and Surlyn 1555ionomer separately (compare Example 4), a result not predicted from U.S.Pat. No. 4,174,335.

                                      TABLE XII                                   __________________________________________________________________________    POWDERS MADE BY DISPERSING BLENDS OF PETROTHENE NA 202                        LOW DENSITY POLYETHYLENE AND SURLYN 1555 IN WATER                             Blend                                                                         Composition       Particle Size Distribution in Weight                        Petro-      Dispersion                                                                          Percent per Particle Size Fraction                          thene   Surlyn                                                                            Time at                                                                             (Microns)                                                      NA 202                                                                             1555                                                                              200° C.,                                                                        53-                                                                              106-                                                                             149-                                                                             250-                                                                             420-                                         No.                                                                              g.   g.  Min.  <53                                                                              106                                                                              149                                                                              250                                                                              420                                                                              600                                                                              >600                                      __________________________________________________________________________    B-1                                                                              136  14  Normal                                                                              No Dispersion                                               B-2                                                                              125  25  Normal                                                                              -- -- -- -- -- 90 --                                        B-2                                                                              125  25  20    -- -- 0.3                                                                              2.1                                                                              21.5                                                                             69.6                                                                             6.1                                       __________________________________________________________________________

EXAMPLE 13

Portions of Blends B-1 and B-2 of Example 12 were dispersed as describedin Examples 4 and 12 but dilute sodium hydroxide solutions were used asthe aqueous medium instead of water. Dispersions were now obtained, withthe particle size distributions shown in Table XIII. At each of the twolevels of Surlyn 1555 employed, finer particles and narrower particlesize distributions were observed for higher initial alkali concentrationin the aqueous medium. A similar effect was observed in Example 3 whenthe degree of neutralization of the ethylene-acrylic acid copolymer wasincreased, indicating again that initial alkali concentration in theaqueous medium is a parameter providing some control over particle size.

The effect on particle size and particle size distribution of increasingthe ionomer/polyethylene ratio was not as evident here in the dispersionof melt-blended resins as it was when the resins were fed separately(Example 4).

                                      TABLE XIII                                  __________________________________________________________________________    POWDERS MADE BY DISPERSING BLENDS OF PETROTHENE NA 202                        AND SURLYN 1555 IN DILUTE AQUEOUS ALKALI MEDIA                                               Aqueous Medium                                                                          450 ml                                                              Dispersion Temp.                                                                       200° C.                                                       Dispersion Time                                                                        Normal                                                                          Particle Size Distribution in Weight                Blend        Aqueous Medium                                                                             Percent per Particle Size                           Petrothene                                                                             Surlyn                                                                            NaOH                                                                              NaOH,                                                                              Na.sup.+,                                                                         Fraction (Microns)                                  Exp.                                                                             NA 202,                                                                             1555,                                                                             Conc.,                                                                            --COOH                                                                             MAA    53-                                                                              106-                                                                             149-                                                                             250-                                    No.                                                                              g.    g.  %   Molar                                                                              Molar                                                                             <53                                                                              106                                                                              149                                                                              250                                                                              420                                                                              >420                                 __________________________________________________________________________    1  136   14  0.055                                                                             0.64 0.79                                                                              21.1.sup.1                                                                       33.3                                                                             21.7                                                                             15.4                                                                             6.5                                                                              1.9                                  2  136   14  0.11                                                                              1.29 1.18                                                                              29.5.sup.1                                                                       44.9                                                                             11.7                                                                             8.8                                                                              3.7                                                                              1.4                                  3  125   25  0.055                                                                             0.36 0.61                                                                              10.6                                                                             31.7                                                                             15.9                                                                             21.9                                                                             10.3                                                                             9.5                                  4  125   25  0.11                                                                              0.72 0.83                                                                              34.9.sup.1                                                                       36.1                                                                             12.2                                                                             11.9                                                                             2.6                                                                              2.2                                  5  125   25  0.22                                                                              1.44 1.26                                                                              42.2.sup.2                                                                       39.5                                                                             14.4                                                                             2.7                                                                              0.8                                                                              0.4                                  __________________________________________________________________________     .sup.1 Microscopic examination showed that out of 100 particles none was      less than 10 microns in diameter (examination made on total powder).          .sup.2 At most 6 particles per 100 had a diameter of 5-10 microns, most       were 20-100 micron particles (examination made on total powder).         

EXAMPLE 14

Additional dispersion experiments were performed with Blends B-1 and B-2of Example 12. Conditions of dispersion were similar to those of Example13 but longer hold times up to 20 minutes at the dispersion temperature(200° C.) were used at two different levels of initial alkaliconcentration in the aqueous medium. Data appear in Table XIV, whichincludes experiments from Table XIII. Overall, the effect of increasedinitial alkali concentration and higher ionomer/polyethylene ratio is tofavor finer particles and some narrowing of particle size distribution.However, there is no advantage in increasing the hold time in theseexperiments in which melt blends of ionomer and polyethylene were fed.Contrasting behavior was observed in dispersing ionomer/EVA blends(Example 11).

                                      TABLE XIV                                   __________________________________________________________________________    POWDERS MADE BY DISPERSING BLENDS OF PETROTHENE NA 202 POLYETHYLENE           AND SURLYN 1555 IN DILUTE AQUEOUS ALKALI MEDIA.                               EFFECT OF DISPERSION TIME                                                                        Aqueous Medium                                                                          450 ml                                                              Dispersion Temp.                                                                       200° C.                                                 Aqueous Medium     Particle Size Distribution in                 Blend Composition                                                                          Init.        Dispersion                                                                          Weight Percent per                            Petrothene                                                                             Surlyn                                                                            NaOH                                                                              NaOH,                                                                              Na.sup.+,                                                                         Time at                                                                             Particle Size Fraction (Microns)              Exp.                                                                             NA 202,                                                                             1555,                                                                             Conc.,                                                                            --COOH                                                                             MAA 200° C.                                                                          53-                                                                              106-                                                                             149-                                                                             250-                                                                             420-                          No.                                                                              g.    g.  %   Molar                                                                              Molar                                                                             Min.  <53.sup.1                                                                         106                                                                              149                                                                              250                                                                              420                                                                              600                           __________________________________________________________________________    1  136   14  0.055                                                                             0.64 0.79                                                                              Normal                                                                              21.1                                                                              33.3                                                                             21.7                                                                             15.4                                                                             6.5                                                                              1.9                           2  136   14  0.055                                                                             0.64 0.79                                                                               5    21.6                                                                              50.0                                                                             14.7                                                                             8.3                                                                              2.9                                                                              2.4                           3  136   14  0.055                                                                             0.64 0.79                                                                              20    21.1                                                                              46.1                                                                             16.3                                                                             14.1                                                                             1.4                                                                              1.0                           4  136   14  0.11                                                                              1.29 1.18                                                                              Normal                                                                              29.5                                                                              44.9                                                                             11.7                                                                             8.8                                                                              3.7                                                                              1.4                           5  136   14  0.11                                                                              1.29 1.18                                                                               5    30.2                                                                              42.6                                                                             12.6                                                                             11.0                                                                             2.4                                                                              1.2                           6  136   14  0.11                                                                              1.29 1.18                                                                              20    30.0                                                                              38.0                                                                             11.8                                                                             12.1                                                                             5.5                                                                              2.6                           7  125   25  0.055                                                                             0.36 0.61                                                                              Normal                                                                              .sup. 10.6.sup.2                                                                  31.7                                                                             15.9                                                                             21.9                                                                             10.3                                                                             9.5                           8  125   25  0.055                                                                             0.36 0.61                                                                              20    23.3                                                                              33.8                                                                             10.9                                                                             22.1                                                                             9.6                                                                              0.2                           9  125   25  0.22                                                                              1.44 1.26                                                                              Normal                                                                              .sup. 42.2.sup.3                                                                  39.5                                                                             14.4                                                                             2.7                                                                              0.8                                                                              0.4                           10 125   25  0.22                                                                              1.44 1.26                                                                               5    .sup. 49.9.sup.4                                                                  34.4                                                                             11.3                                                                             2.9                                                                              1.0                                                                              0.5                           11 125   25  0.22                                                                              1.44 1.26                                                                              10    .sup. 45.2.sup.3                                                                  32.9                                                                             17.6                                                                             3.2                                                                              0.7                                                                              0.4                           12 125   25  0.22                                                                              1.44 1.26                                                                              20    .sup. 50.9.sup.5                                                                  30.6                                                                             12.0                                                                             5.1                                                                              1.1                                                                              0.2                           __________________________________________________________________________     .sup.1 Microscopic examination showed that each of the total powders was      free of particles with a diameter of 10 microns or less, except where         noted otherwise; most particles were 20-100 microns in diameter.              .sup.2 Not examined.                                                          .sup.3 At most 6 particles out of 100 had a diameter of 5-10 microns; mos     particles had a diameter of 20-100 microns (examination on total powder).     .sup.4 Out of 100 particles 4 had diameters of 5-10 microns; most             particles had diameters of 20-100 microns (examination on total powder).      .sup.5 1-2 particles per 100 had diameters of 5-10 microns; most were         20-100 micron particles (examination on total powder).                   

EXAMPLE 15

In this example a blend of 10 parts by weight of Surlyn 1555 and 100parts by weight of Vynathene EY 901 ethylene-vinyl acetate copolymer wasmade on a two-roll mill by milling the two resins together for 5 minutesat 113° C. In three experiments, 150 g portions of the blend were cutinto small pieces and charged to the reactor along with 450 ml. of a0.22 weight percent aqueous solution of sodium hydroxide. Dispersionexperiments were performed according to the general dispersionprocedure, but three different dispersion temperatures were employed,and a 20-minute hold time was applied at each dispersion temperaturebefore cooling to 100° C. in the normal way. Table XV records theresults of the experiments.

Under the conditions of these experiments, increasing the dispersingtemperature from 150° C. to 200° C. narrowed the particle sizedistribution to an intermediate particle size range (149-420 microns).

                  TABLE XV                                                        ______________________________________                                        Powders Made by Dispersing Blends                                             of Vynathene EY 901 Ethylene-Vinyl                                            Acetate Copolymer and Surlyn 1555                                             in Dilute Aqueous Alkali Medium.                                              Effect of Dispersion Temperature at                                           a 20 Minute Hold Time                                                         Vynathene EY 901      136 g                                                   Surlyn 1555            14 g                                                   Aqueous Medium        450 ml                                                  Init. NaOH Conc.      0.22 wt. %                                              NaOH/--COOH           2.6 (molar)                                             Na.sup.+ /MAA         1.9 (molar)                                             Dispersion Time       20 min.                                                        Particle Size Distribution in Weight Percent                                  per Particle Size Fraction (Microns)                                   Dispersion      53-     106- 149-  250- 420-                                  Temp. °C.                                                                       <53    106     149  250   420  600   >600                            ______________________________________                                        150      3.0    15.1    9.0  17.5  18.6 22.5  14.3                            175      4.0    12.6    10.0 13.4  20.7 22.5  16.8                            200      2.4    10.1    10.0 28.6  44.0 4.6   0.1                             ______________________________________                                    

EXAMPLE 16

As in Example 15, a blend of 10 parts by weight of Surlyn 1555 and 100parts by weight of Vynathene EY 901, ethylene-vinyl acetate copolymerwas dispersed in dilute aqueous alkali media in a series of experimentsat 200° C. in which the effect of longer hold times of 5, 10 and 20minutes was investigated (Table XVI).

Under the conditions of the experiments, the particle size distributionnarrows with increasing hold time at the dispersion temperature, but thedistribution centers not in the finest particles ranges, but atintermediate particle sizes, i.e., at 149-420 microns. There is nosignificant increase in the finest particle fraction (<53 microns).Accordingly, the ethylene-vinyl acetate copolymer and low densitypolyethylene respond differently to increased hold time at dispersiontemperature and, at least for ethylene-vinyl acetate copolymers, holdtime can be used as a means of exerting control over particle size.

                  TABLE XVI                                                       ______________________________________                                        Powders Made By Dispersing Blends                                             of Vynathene EY 901 Ethylene-Vinyl                                            Acetate Copolymer and Surlyn 1555                                             in Dilute Aqueous Alkali Medium.                                              Effect of Dispersion Hold Time at                                             200° C.                                                                Vynathene EY 901      136 g                                                   Surlyn 1555            14 g                                                   Aqueous Medium        450 ml                                                  Init. NaOH Conc.      0.22 wt. %                                              NaOH/--COOH           2.6 (molar)                                             Na.sup.+ /MAA         1.9 (molar)                                             Dispersion Temp.      200° C.                                                     Particle Size Distribution in Weight Percent                       Dispersion per Particle Size Fraction (Microns)                               Exp. Time,            53-  106- 149-  250- 420-                               No.  min.      <53    106  149  250   420  600  >600                          ______________________________________                                        1    Normal    1.7    10.1 6.2  14.6  19.0 20.8 27.7                          2     5        2.2    12.5 10.1 15.2  22.6 28.9 8.5                           3    10        2.4    7.2  9.2  25.1  44.8 10.7 0.6                           4    20        3.4    10.2 15.0 40.4  29.6 0.9  0.4                           ______________________________________                                    

EXAMPLE 17

A melt blend of Petrothene LS 630 (250 g) and Surlyn 1555 (13.2 g) wasmade on a two-roll mill at 135° C. A 150 g portion of the blend (142.5 gPetrothene LS 630 and 7.5 g of Surlyn 1555) was cut into pieces andintroduced into the Parr pressure reactor along with 450 ml of watercontaining 0.17 g of sodium hydroxide. In accordance with the generaldispersion procedure, the reactor was heated to 200° C., when stirringat 3700 rpm was started. Cooling of the reactor with dry ice was startedat once and the stirring was continued until the temperature reaced 100°C. The product was a coarse dispersion with the following particle sizedistribution:

    ______________________________________                                         53-106 microns,    2-8% by weight                                            106-149 microns,    13.1% by weight                                           149-250 microns,    26.2% by weight                                           250-420 microns,    33.2% by weight                                           >420 microns,       24.7% by weight                                           ______________________________________                                    

The conditions of the above experiment closely resemble those of Example2, U.S. Pat. No. 4,174,335 in prior melt blending of resins, ratio ofthermoplastic resin to dispersing resin, acid number and degree ofneutralization of dispersing resin. Linear polyethylene, however, wassubstituted for ethylene-butene-1 copolymer as thermoplastic resin. But,more importantly, the slow addition rate of the above cited patent wasreplaced with the rapid resin feed rate of the present invention (TablesA-2, B-2).

The experiment shows that the ultrafine particles of U.S. Pat. No.4,174,335 are not obtained. Instead, the coarser particles of theprocess of this invention are recovered.

EXAMPLE 18

Powder products made by dispersing Vynathene EY 901 ethylene-vinylacetate copolymer with 10 and 20 parts by weight of Surlyn 1555 per 100parts of the copolymer were milled for 5 minutes at 113° C. in atwo-roll rubber mill, and then pressed into test plaques at 140° C. for3 minutes. Strength properties were determined on these test specimens.In addition, similar compositions were made by mixing the two resins inthe same proportions on a two-roll mill, and the strength properties ofthe mill blends were determined for comparison. Melt flow rates of thevarious compositions were also measured. Corresponding measurements weremade on both the Surlyn 1555 and Vynathene EY 901. Results are tabulatedin Table XVIII.

The data in Table XVIII show that the tensile strength of the blends ofVynathene EY 901 and Surlyn 1555 fall in the range of 2,000-2,200 psiwhen made by the powder process described hereinbefore. Simple millblends of the same composition exhibit tensile strengths that aresomewhat lower, i.e., in the range 1,700-2,000 psi. The tensilestrengths of the original Vynathene EY 901 and Surlyn 1555 weredetermined and a straight line drawn between the two values as referencepoints (Table XVIII) as a function of blend composition. Tensile valueswere interpolated along the line corresponding to the powder and millblend compositions and are set forth in Table XVIII along with themeasured tensile strengths. For all blends, the measured tensiles arehigher than the interpolated tensiles with those of the powder processblends exceeding the values for the mill blends.

Blend specimens showing the above described elevated tensile strengthwere tested for gel content. It was found that all such compositionswere soluble in the hot tetrahydrofuran containing 5% glacial aceticacid.

                                      TABLE XVIII                                 __________________________________________________________________________    COMPARISON OF THE PROPERTIES OF COMPOSITIONS MADE ON A TWO ROLL MILL          WITH THOSE OF COMPOSITIONS MADE BY POWDER PROCESS                                                      Properties of Product.sup.1                                                   Melt Flow                                                                           Tensile Strength,                                       Surlyn                                                                            Compounding Method                                                                        Rate, Break, psi           Gel                       Exp.                                                                             Vynathene                                                                           1555        Temp.,                                                                            (Cond. B)                                                                           Inter-     Elong.                                                                            Hardness,                                                                           Content                   No.                                                                              EY 901                                                                              pph Type    °C.                                                                        g/10 Min.                                                                           polated.sup.2                                                                      Measured.sup.3                                                                      %.sup.3                                                                           Shore A.sup.4                                                                       %.sup.5                   __________________________________________________________________________    1  Specimen 1                                                                          None                                                                              None    --  1.40  --   1,408 798 67    --                        2  Specimen 1                                                                          None                                                                              Mill 5 minutes                                                                        150 1.40  --   1,730 797 --    --                        3  Specimen 1                                                                          10  Mill 5 minutes                                                                        150 1.28  1,510                                                                              1,994 887 68    --                        4  Specimen 1                                                                          20  Mill 5 minutes                                                                        150 1.22  1,600                                                                              1,895 873 71    --                        5  Specimen 1                                                                          20  Mill 5 minutes                                                                        182 1.30  1,606                                                                              1,819 882 72    --                        6  Specimen 1                                                                          10  Powder Process                                                                        200 0.59  1,510                                                                              2,103 760 73    zero                      7  Specimen 1                                                                          20  Powder Process                                                                        200 0.42  1,600                                                                              2,204 742 79    zero                      8  Specimen 2                                                                          None                                                                              None    --  1.48  --   1,410 766 --    --                        9  Specimen 2                                                                          10  Mill 5 minutes                                                                        150 1.35  1,510                                                                              1,925 854 --    --                        10 Specimen 2                                                                          20  Mill 5 minutes                                                                        150 1.26  1,600                                                                              1,700 860 --    --                        11 Specimen 2                                                                          20  Mill 5 minutes                                                                        200 0.94  1,600                                                                              1,749 860 --    --                        12 Specimen 2                                                                          10  Powder Process                                                                        200 0.60  1,510                                                                              2,096 858 --    --                        13 Specimen 2                                                                          20  Powder Process                                                                        200 0.61  1,600                                                                              1,995 853 --    --                        14 Specimen 3                                                                          None                                                                              None    --  0.48  --   1,620     --    --                        15 None  100 None    --  0.59  --   2,608     --    --                        __________________________________________________________________________     .sup.1 All products were pressed into test plaques at 140° C. and      500 psi for 3 minutes. To avoid heterogeneity, powder process products        were first milled 5 minutes at 113° C.                                 .sup.2 Interpolation on straight line joining measured ring tensiles of       EVA and of Surlyn 1555.                                                       .sup.3 Tensiles were measured on ring test specimens by a procedure           similiar to ASTM D412.                                                        .sup.4 ASTM D2240                                                             .sup.5 As judged by solubility in a mixture of tetrahydrofuran containing     5% by weight: of glacial acetic acid.                                    

EXAMPLE 19

In this example, Vynathene EY 901 ethylene-vinyl acetate copolymer wasdispersed in water in two separate experiments with 10 parts and with 20parts by weight of Surlyn 1555 as described in Example 8 (Experiments 1and 2 of Table VIII). Upon recovery, the ionomer polymer-coated powders,compositions which exhibit elevated tensile strengths characteristic ofthermoplastic elastomers as disclosed hereinabove, were then tested asimpact modifiers in rigid polyvinyl chloride as follows:

Each powder was dry-blended with polyvinyl chloride powder (Geon 100EP-76F, B. F. Goodrich Company) and stabilizers Mark C and Mark 235 (abarium/cadmium type and a phosphite type, respectively, Argus ChemicalCorporation) in the amounts shown in Table XIX (Compounds A and B). Thetwo powder blends were milled for 10 minutes at 195±5° C. on a two-rollmill. The milled compounds were thereafter compression molded into6-inch×6-inch×1/8-inch sheets at about 190° C. Test specimens were cutfrom the sheets and finished on a milling machine to the desireddimensions. Physical properties were then determined on the specimensand are reported in Table XIX. A control compound (Compound C) was madeunder the same conditions, except that in place of the ionomer-coatedethylene-vinyl acetate copolymers, pellets of the same ethylene-vinylacetate copolymer were substituted. Table XIX shows that the Izod impactstrengths of the test specimens made from Compounds A and B comparedwell with the Izod impact obtained from the control Compound C.Stiffness properties were somewhat inferior, but this may, in part,reflect the fact that the powders were compared at equal levels ofethylene-vinyl acetate copolymers; i.e., the total amounts of powder waslarger by the amount of ionomer resin present.

                                      TABLE XIX                                   __________________________________________________________________________                           Compound                                                               Test Method                                                                          A     B    C                                           __________________________________________________________________________    Geon 103EP-76F         100   100  100                                         Mark C                 1     1    1                                           Mark 235               3     3    3                                           Ethylene-vinyl acetate                                                        Powder with 10 phr Surlyn 1555                                                                       8.9    --   --                                         Powder with 20 phr Surlyn 1555                                                                        --   10    --                                         Pellets                 --    --  8                                           Time to Band, sec.     120   135  115                                         Plate-out              Very slight                                                                         Moderate                                                                           Slight                                      Izod Impact Strength                                                                          ASTM D256                                                     Ft-Lbs/inch of notch,  18.5  17.7 18.7                                        Room Temperature                                                              0° C.           2.2   2.2  3.1                                         Falling Weight Impact Strength                                                                ASTM D3029                                                    In-lbs/mil, Room Temp. 3.71  3.81 3.74                                        Heat Distortion Temp. at 264                                                                  ASTM D648                                                                            68.0  67.8 67.8                                        psi, °C.                                                               Hardness, Shore D, 15 sec.                                                                    ASTM D2240                                                                           66.9  77.5 78                                          Flexural Strength, psi                                                                        ASTM D790                                                                            12,533                                                                              10,330                                                                             11,980                                      Flexural Stiffness, psi                                                                       ASTM D790                                                                            326,766                                                                             323,984                                                                            383,937                                     __________________________________________________________________________

What is claimed is:
 1. A dry powder of finely dispersed thermoplasticresin comprising resins selected from homopolymers and copolymers ofolefins wherein the individual resin particles are substantially coateduniformly with a substantially water-insoluble ionomer, the ionomerincluding at least about 50 mol percent of an ethylenically unsaturatedalpha-olefin of about 2 to about 10 carbon atoms, from about 0.2 toabout 50 mol percent of an alpha, beta ethylenically unsaturatedcarboxylic acid having from about 3 to about 8 carbon atoms, with atleast 10% of the acid groups being neutralized, said individual resinparticles having diameters greater than about 10 microns and beingpresent in the form of a finely divided dry powder.
 2. The thermoplasticresin of claim 1 wherein the individual particles have diameters lessthan about 800 microns and greater than about 10 microns.
 3. Thethermoplastic resin of claim 1 wherein the ionomer polymer is made bysalt-forming with metal ions at least 10% of the acid groups of acopolymer of units derived from an alpha-olefin of the formula RCH═CH₂wherein R is H or alkyl having from 1-8 carbon atoms and from 1.0 to 25mole percent of units derived from an alpha, beta-ethylenicallyunsaturated carboxylic acid selected from the group consisting of alpha,beta-ethylenically unsaturated carboxylic acids consisting of acrylicacid, methacrylic acid, maleic acid and, fumaric acid.
 4. Thethermoplastic resin of claim 3 wherein said alpha-olefin is ethylene. 5.The thermoplastic resin of claim 3 wherein said alpha,beta-ethylenically unsaturated carboxylic acid is methacrylic acid. 6.The thermoplastic resin of claim 1 wherein the homopolymer is selectedfrom the group consisting of polyethylene, polypropylene, polybutene,polyisobutylene and poly(4-methylpentene).
 7. The thermoplastic resin ofclaim 6 wherein the homopolymer is polyethylene or polypropylene.
 8. Thethermoplastic resin of claim 1 wherein the copolymer is selected fromthe group consisting of ethylene-vinyl acetate, ethylene-vinylpropionate, ethylene-vinyl isobutyrate, ethylene-vinyl alcohol,ethylene-methyl acrylate, and ethylene-ethyl methacrylate.
 9. Thethermoplastic resin of claim 8 wherein the copolymer is ethylene-vinylacetate.
 10. The thermoplastic resin of claim 9 wherein saidethylene-vinyl acetate copolymer comprises between about 25 to 50 weightpercent of said copolymer of ethylene.
 11. Impact modifier powderssuitable for dry blending into rigid polyvinyl chloride powderformulations in accordance with claim 1 wherein said modifier powderscomprise from about ten to about twenty parts by weight of ionomer resinper one hundred parts by weight ethylene-vinyl acetate copolymer. 12.The thermoplastic resin of claim 11 wherein the ionomer polymer is madeby salt forming with metal ions at least 10% of the acid groups of acopolymer of units derived from an alpha-olefin of the formula RCH═CH₂wherein R is H or alkyl having from 1-8 carbon atoms and from 1.0 to 25mole percent of units derived from an alpha, beta-ethylenicallyunsaturated carboxylic acid selected from the group consisting of alpha,beta-ethylenically unsaturated carboxylic acids consisting of acrylicacid, methacrylic acid, maleic acid and, fumaric acid.
 13. Thethermoplastic resin of claim 12 wherein said alpha-olefin is ethylene.14. The thermoplastic resin of claim 12 wherein said alpha,beta-ethylenically unsaturated carboxylic acid is methacrylic acid. 15.The thermoplastic resin of claim 1 wherein the copolymer is selectedfrom the group consisting of olefin-allyl copolymers.
 16. Thethermoplastic resin of claim 15 wherein said olefin-allyl copolymer isselected from the group consisting of ethylene-allyl alcohol,ethylene-allyl acetate, ethylene-allyl ether and ethylene-acrolein.